ESB-2018.0900 - [Cisco] Cisco IOS and Cisco IOS XE: Denial of service - Remote/unauthenticated 2018-03-29

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2018.0900
    Cisco IOS and IOS XE Software DHCP Version 4 Relay Vulnerabilities
                               29 March 2018

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Cisco IOS
                   Cisco IOS XE
Publisher:         Cisco Systems
Operating System:  Cisco
Impact/Access:     Denial of Service -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2018-0174 CVE-2018-0173 CVE-2018-0172

Original Bulletin: 
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr1
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr2
   https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr3

Comment: This bulletin contains three (3) security advisories.

- --------------------------BEGIN INCLUDED TEXT--------------------

Cisco Security Advisory

Cisco IOS and IOS XE Software DHCP Version 4 Relay Heap Overflow Denial of
Service Vulnerability

High

Advisory ID:     cisco-sa-20180328-dhcpr1

First Published: 2018 March 28 16:00 GMT

Version 1.0:     Final

Workarounds:     No workarounds available

Cisco Bug IDs:
CSCvg62730

CVE-2018-0172

CWE-20

CVSS Score:
8.6  AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X

Summary

  o A vulnerability in the DHCP option 82 encapsulation functionality of
    Cisco IOS Software and Cisco IOS XE Software could allow an
    unauthenticated, remote attacker to cause an affected device to reload,
    resulting in a denial of service (DoS) condition.

    The vulnerability exists because the affected software performs incomplete
    input validation of option 82 information that it receives in DHCP Version
    4 (DHCPv4) packets from DHCP relay agents. An attacker could exploit this
    vulnerability by sending a crafted DHCPv4 packet to an affected device. A
    successful exploit could allow the attacker to cause a heap overflow
    condition on the affected device, which will cause the device to reload and
    result in a DoS condition.

    Cisco has released software updates that address this vulnerability. There
    are no workarounds that address this vulnerability.

    This advisory is available at the following link:
    https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
    cisco-sa-20180328-dhcpr1

    This advisory is part of the March 28, 2018, release of the Cisco IOS and
    IOS XE Software Security Advisory Bundled Publication, which includes 20
    Cisco Security Advisories that describe 22 vulnerabilities. For a complete
    list of the advisories and links to them, see Cisco Event Response: March
    2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
    Publication.

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco devices that meet all the following
    criteria:

       The device is running a vulnerable release of Cisco IOS Software or
        Cisco IOS XE Software. For information about which Cisco IOS and IOS XE
        Software releases are vulnerable, see the Fixed Software section of
        this advisory.
       An interface of the device is configured as a DHCP relay agent.
       The device or an interface of the device is configured to insert DHCP
        relay agent information (option 82 information) into DHCP packets.
       The device or an interface of the device is configured to encapsulate
        option 82 information that it receives from other DHCP relay agents.

    Assessing the DHCP Relay Agent Configuration

    To determine whether any interfaces of a device are configured as a DHCP
    relay agent, administrators can log in to the device and use the show
    running-config | include ip helper-address command in the CLI. If the
    device is a Cisco cBR-8 Converged Broadband Router, administrators should
    instead use the show running-config | include cable helper-address command
    in the CLI.

    If the command returns output, at least one interface of the device is
    configured as a DHCP relay agent.

    The following example shows the output of the show running-config | include
    ip helper-address command for a device that is running Cisco IOS Software
    and has an interface that is configured to act as a DHCP relay agent and
    forward DHCP packets to the DHCP server address 10.10.10.1:

        Router# show running-config | include ip helper-address

        ip helper-address  10.10.10.1
        Router#

    If the show running-config | include ip helper-address command, or the show
    running-config | include cable helper-address command on a Cisco cBR-8
    Router, does not return any output, none of the interfaces of the device
    are configured as a DHCP relay agent.

    Assessing Support for Option 82 Insertion

    To determine whether a device or an interface of a device is configured to
    insert option 82 information into DHCP packets, administrators can log in
    to the device and use the show running-config | include ip dhcp relay
    information option command in the CLI.

    If the command output contains any of the following, the device is
    configured to insert option 82 information into DHCP packets:

       ip dhcp relay information option-insert--Interface configuration,
        appears under the interface that is configured as a DHCP relay agent
       ip dhcp relay information option server-id-override--Interface
        configuration, appears under the interface that is configured as a DHCP
        relay agent
       ip dhcp relay information option--Global configuration

    The following example shows the output of the show running-config | include
    ip dhcp relay information option command for a device that is running
    Cisco IOS Software and has an interface that is configured to both act as a
    DHCP relay agent and insert option 82 information into DHCP packets:

        Router# show running-config | include ip dhcp relay information option

        ip dhcp relay information option-insert
        Router#

    If the show running-config | include ip dhcp relay information option
    command does not return any output, neither the device nor any interfaces
    of the device are configured to insert option 82 information into DHCP
    packets.

    Assessing Support for Option 82 Encapsulation

    To determine whether a device or an interface of a device is configured to
    encapsulate DHCP option 82 information that it receives from other DHCP
    relay agents, administrators can log in to the device and use the show
    running-config | include ip dhcp relay information policy.* encapsulate
    command in the CLI.

    If the command output contains either of the following, the device is
    configured to encapsulate option 82 information that it receives:

       ip dhcp relay information policy-action encapsulate--Interface
        configuration, appears under the interface that is configured as a DHCP
        relay agent
       ip dhcp relay information policy encapsulate--Global configuration

    The following example shows the output of the command for a device that is
    running Cisco IOS Software and is configured to both act as a DHCP relay
    agent and encapsulate option 82 information that it receives from other
    DHCP relay agents:

        Router# show running-config | include ip dhcp relay information policy.* encapsulate

        ip dhcp relay information policy encapsulate
        Router#

    If the show running-config | include ip dhcp relay information
    policy.* encapsulate command does not return any output, neither the device
    nor any interfaces of the device are configured to encapsulate option 82
    information.

    Determining the Cisco IOS Software Release

    To determine which Cisco IOS Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS Software, the system banner displays text similar to
    Cisco Internetwork Operating System Software or Cisco IOS Software. The
    banner also displays the installed image name in parentheses, followed by
    the Cisco IOS Software release number and release name. Some Cisco devices
    do not support the show version command or may provide different output.

    The following example shows the output of the command for a device that is
    running Cisco IOS Software Release 15.5(2)T1 and has an installed image
    name of C2951-UNIVERSALK9-M:

        Router> show version

        Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2015 by Cisco Systems, Inc.
        Compiled Mon 22-Jun-15 09:32 by prod_rel_team
        .
        .
        .

    For information about the naming and numbering conventions for Cisco IOS
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Determining the Cisco IOS XE Software Release

    To determine which Cisco IOS XE Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS XE Software, the system banner displays Cisco IOS
    Software, Cisco IOS XE Software, or similar text.

    The following example shows the output of the command for a device that is
    running Cisco IOS XE Software Release 16.2.1 and has an installed image
    name of CAT3K_CAA-UNIVERSALK9-M:

        ios-xe-device# show version

        Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2016 by Cisco Systems, Inc.
        Compiled Sun 27-Mar-16 21:47 by mcpre
        .
        .
        .

    For information about the naming and numbering conventions for Cisco IOS XE
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Products Confirmed Not Vulnerable

    No other Cisco products are currently known to be affected by this
    vulnerability.

    Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
    Software or Cisco NX-OS Software.

Details

  o To exploit this vulnerability, exploit packets would need to be received
    via an interface that meets all the configuration requirements outlined in
    the Vulnerable Products section of this advisory.

Workarounds

  o There are no workarounds that address this vulnerability.

Fixed Software

  o Cisco has released free software updates that address the vulnerability
    described in this advisory. Customers may only install and expect support
    for software versions and feature sets for which they have purchased a
    license. By installing, downloading, accessing, or otherwise using such
    software upgrades, customers agree to follow the terms of the Cisco
    software license:
    https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

    Additionally, customers may only download software for which they have a
    valid license, procured from Cisco directly, or through a Cisco authorized
    reseller or partner. In most cases this will be a maintenance upgrade to
    software that was previously purchased. Free security software updates do
    not entitle customers to a new software license, additional software
    feature sets, or major revision upgrades.

    When considering software upgrades, customers are advised to regularly
    consult the advisories for Cisco products, which are available from the
    Cisco Security Advisories and Alerts page, to determine exposure and a
    complete upgrade solution.

    In all cases, customers should ensure that the devices to be upgraded
    contain sufficient memory and confirm that current hardware and software
    configurations will continue to be supported properly by the new release.
    If the information is not clear, customers are advised to contact the Cisco
    Technical Assistance Center (TAC) or their contracted maintenance
    providers.

    Customers Without Service Contracts

    Customers who purchase directly from Cisco but do not hold a Cisco service
    contract and customers who make purchases through third-party vendors but
    are unsuccessful in obtaining fixed software through their point of sale
    should obtain upgrades by contacting the Cisco TAC:
    https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

    Customers should have the product serial number available and be prepared
    to provide the URL of this advisory as evidence of entitlement to a free
    upgrade.

    Cisco IOS and IOS XE Software

    To help customers determine their exposure to vulnerabilities in Cisco IOS
    and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker,
    that identifies any Cisco Security Advisories that impact a specific
    software release and the earliest release that fixes the vulnerabilities
    described in each advisory ("First Fixed"). If applicable, the tool also
    returns the earliest release that fixes all the vulnerabilities described
    in all the advisories identified ("Combined First Fixed").

    Customers can use this tool to perform the following tasks:

       Initiate a search by choosing one or more releases from a drop-down
        list or uploading a file from a local system for the tool to parse
       Enter the output of the show version command for the tool to parse
       Create a custom search by including all previously published Cisco
        Security Advisories, a specific advisory, or all advisories in the most
        recent bundled publication

    To determine whether a release is affected by any published Cisco Security
    Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a
    Cisco IOS Software or Cisco IOS XE Software release--for example, 15.1(4)M2
    or 3.13.8S--in the following field:

    [                    ] [Check]

    For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
    releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S
    Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the
    Cisco IOS XE Software release.

Exploitation and Public Announcements

  o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
    any public announcements or malicious use of the vulnerability that is
    described in this advisory.

Source

  o Cisco would like to thank Tenable for finding and reporting this
    vulnerability.

Cisco Security Vulnerability Policy

  o To learn about Cisco security vulnerability disclosure policies and
    publications, see the Security Vulnerability Policy. This document also
    contains instructions for obtaining fixed software and receiving security
    vulnerability information from Cisco.

Subscribe to Cisco Security Notifications

  o Subscribe

Related to This Advisory

  o Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software
    Security Advisory Bundled Publication
    Cisco Security Blog: Cisco IOS and IOS XE Software Bundled Publication
    March 2018

URL

  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr1

Revision History

  o 
    +----------+----------------------------+----------+---------+----------------+
    | Version  |        Description         | Section  | Status  |      Date      |
    +----------+----------------------------+----------+---------+----------------+
    | 1.0      | Initial public release.    | --       | Final   | 2018-March-28  |
    +----------+----------------------------+----------+---------+----------------+


======================================================

Cisco Security Advisory

Cisco IOS and IOS XE Software DHCP Version 4 Relay Reply Denial of Service
Vulnerability

High

Advisory ID:     cisco-sa-20180328-dhcpr2

First Published: 2018 March 28 16:00 GMT

Version 1.0:     Final

Workarounds:     No workarounds available

Cisco Bug IDs:
CSCvg62754

CVE-2018-0173

CWE-20

CVSS Score:
8.6  AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X

Summary

  o A vulnerability in the Cisco IOS Software and Cisco IOS XE Software
    function that restores encapsulated option 82 information in DHCP Version
    4 (DHCPv4) packets could allow an unauthenticated, remote attacker to cause
    an affected device to reload, resulting in a denial of service (DoS)
    condition.

    The vulnerability exists because the affected software performs incomplete
    input validation of encapsulated option 82 information that it receives in
    DHCPOFFER messages from DHCPv4 servers. An attacker could exploit this
    vulnerability by sending a crafted DHCPv4 packet to an affected device,
    which the device would then forward to a DHCPv4 server. When the affected
    software processes the option 82 information that is encapsulated in the
    response from the server, an error could occur. A successful exploit could
    allow the attacker to cause the affected device to reload, resulting in a
    DoS condition.

    Cisco has released software updates that address this vulnerability. There
    are no workarounds that address this vulnerability.

    This advisory is available at the following link:
    https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
    cisco-sa-20180328-dhcpr2

    This advisory is part of the March 28, 2018, release of the Cisco IOS and
    IOS XE Software Security Advisory Bundled Publication, which includes 20
    Cisco Security Advisories that describe 22 vulnerabilities. For a complete
    list of the advisories and links to them, see Cisco Event Response: March
    2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
    Publication.

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco devices that meet all the following
    criteria:

       The device is running a vulnerable release of Cisco IOS Software or
        Cisco IOS XE Software. For information about which Cisco IOS and IOS XE
        Software releases are vulnerable, see the Fixed Software section of
        this advisory.
       The device is part of a network environment in which the DHCP server is
        configured to support use of DHCP relay agent information (option 82
        information) in DHCP packets that it receives and sends. Validation of
        server support for option 82 information is server dependent.
       An interface of the device is configured as a DHCP relay agent.
       The device or an interface of the device is configured to insert option
        82 information into DHCP packets.

    Assessing the DHCP Relay Agent Configuration

    To determine whether any interfaces of a device are configured as a DHCP
    relay agent, administrators can log in to the device and use the show
    running-config | include ip helper-address command in the CLI. If the
    device is a Cisco cBR-8 Converged Broadband Router, administrators should
    instead use the show running-config | include cable helper-address command
    in the CLI.

    If the command returns output, at least one interface of the device is
    configured as a DHCP relay agent.

    The following example shows the output of the show running-config | include
    ip helper-address command for a device that is running Cisco IOS Software
    and has an interface that is configured to act as a DHCP relay agent and
    forward DHCP packets to the DHCP server address 10.10.10.1:

        Router# show running-config | include ip helper-address

        ip helper-address  10.10.10.1
        Router#

    If the show running-config | include ip helper-address command, or the show
    running-config | include cable helper-address command on a Cisco cBR-8
    Router, does not return any output, none of the interfaces of the device
    are configured as a DHCP relay agent.

    Assessing Support for Option 82 Insertion

    To determine whether a device or an interface of a device is configured to
    insert option 82 information into DHCP packets, administrators can log in
    to the device and use the show running-config | include ip dhcp relay
    information option command in the CLI.

    If the command output contains any of the following, the device is
    configured to insert option 82 information into DHCP packets:

       ip dhcp relay information option-insert--Interface configuration,
        appears under the interface that is configured as a DHCP relay agent
       ip dhcp relay information option server-id-override--Interface
        configuration, appears under the interface that is configured as a DHCP
        relay agent
       ip dhcp relay information option--Global configuration

    The following example shows the output of the show running-config | include
    ip dhcp relay information option command for a device that is running
    Cisco IOS Software and has an interface that is configured to both act as a
    DHCP relay agent and insert option 82 information into DHCP packets:

        Router# show running-config | include ip dhcp relay information option

        ip dhcp relay information option-insert
        Router#

    If the show running-config | include ip dhcp relay information option
    command does not return any output, neither the device nor any interfaces
    of the device are configured to insert option 82 information into DHCP
    packets.

    Determining the Cisco IOS Software Release

    To determine which Cisco IOS Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS Software, the system banner displays text similar to
    Cisco Internetwork Operating System Software or Cisco IOS Software. The
    banner also displays the installed image name in parentheses, followed by
    the Cisco IOS Software release number and release name. Some Cisco devices
    do not support the show version command or may provide different output.

    The following example shows the output of the command for a device that is
    running Cisco IOS Software Release 15.5(2)T1 and has an installed image
    name of C2951-UNIVERSALK9-M:

        Router> show version

        Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2015 by Cisco Systems, Inc.
        Compiled Mon 22-Jun-15 09:32 by prod_rel_team
        .
        .
        .

    For information about the naming and numbering conventions for Cisco IOS
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Determining the Cisco IOS XE Software Release

    To determine which Cisco IOS XE Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS XE Software, the system banner displays Cisco IOS
    Software, Cisco IOS XE Software, or similar text.

    The following example shows the output of the command for a device that is
    running Cisco IOS XE Software Release 16.2.1 and has an installed image
    name of CAT3K_CAA-UNIVERSALK9-M:

        ios-xe-device# show version

        Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2016 by Cisco Systems, Inc.
        Compiled Sun 27-Mar-16 21:47 by mcpre
        .
        .
        .

    For information about the naming and numbering conventions for Cisco IOS XE
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Products Confirmed Not Vulnerable

    No other Cisco products are currently known to be affected by this
    vulnerability.

    Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
    Software or Cisco NX-OS Software.

Details

  o To exploit this vulnerability, exploit packets would need to be received
    via an interface that meets all the configuration requirements outlined in
    the Vulnerable Products section of this advisory.

Indicators of Compromise

  o Exploitation of this vulnerability could cause a segmentation fault in the
    DHCPD Receive process on an affected device. Contact your support
    organization to review the stack trace and determine whether the device has
    been compromised by exploitation of this vulnerability.

Workarounds

  o There are no workarounds that address this vulnerability.

Fixed Software

  o Cisco has released free software updates that address the vulnerability
    described in this advisory. Customers may only install and expect support
    for software versions and feature sets for which they have purchased a
    license. By installing, downloading, accessing, or otherwise using such
    software upgrades, customers agree to follow the terms of the Cisco
    software license:
    https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

    Additionally, customers may only download software for which they have a
    valid license, procured from Cisco directly, or through a Cisco authorized
    reseller or partner. In most cases this will be a maintenance upgrade to
    software that was previously purchased. Free security software updates do
    not entitle customers to a new software license, additional software
    feature sets, or major revision upgrades.

    When considering software upgrades, customers are advised to regularly
    consult the advisories for Cisco products, which are available from the
    Cisco Security Advisories and Alerts page, to determine exposure and a
    complete upgrade solution.

    In all cases, customers should ensure that the devices to be upgraded
    contain sufficient memory and confirm that current hardware and software
    configurations will continue to be supported properly by the new release.
    If the information is not clear, customers are advised to contact the Cisco
    Technical Assistance Center (TAC) or their contracted maintenance
    providers.

    Customers Without Service Contracts

    Customers who purchase directly from Cisco but do not hold a Cisco service
    contract and customers who make purchases through third-party vendors but
    are unsuccessful in obtaining fixed software through their point of sale
    should obtain upgrades by contacting the Cisco TAC:
    https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

    Customers should have the product serial number available and be prepared
    to provide the URL of this advisory as evidence of entitlement to a free
    upgrade.

    Cisco IOS and IOS XE Software

    To help customers determine their exposure to vulnerabilities in Cisco IOS
    and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker,
    that identifies any Cisco Security Advisories that impact a specific
    software release and the earliest release that fixes the vulnerabilities
    described in each advisory ("First Fixed"). If applicable, the tool also
    returns the earliest release that fixes all the vulnerabilities described
    in all the advisories identified ("Combined First Fixed").

    Customers can use this tool to perform the following tasks:

       Initiate a search by choosing one or more releases from a drop-down
        list or uploading a file from a local system for the tool to parse
       Enter the output of the show version command for the tool to parse
       Create a custom search by including all previously published Cisco
        Security Advisories, a specific advisory, or all advisories in the most
        recent bundled publication

    To determine whether a release is affected by any published Cisco Security
    Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a
    Cisco IOS Software or Cisco IOS XE Software release--for example, 15.1(4)M2
    or 3.13.8S--in the following field:

    [                    ] [Check]

    For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
    releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S
    Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the
    Cisco IOS XE Software release.

Exploitation and Public Announcements

  o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
    any public announcements or malicious use of the vulnerability that is
    described in this advisory.

Source

  o Cisco would like to thank Tenable for finding and reporting this
    vulnerability.

Cisco Security Vulnerability Policy

  o To learn about Cisco security vulnerability disclosure policies and
    publications, see the Security Vulnerability Policy. This document also
    contains instructions for obtaining fixed software and receiving security
    vulnerability information from Cisco.

Subscribe to Cisco Security Notifications

  o Subscribe

Related to This Advisory

  o Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software
    Security Advisory Bundled Publication
    Cisco Security Blog: Cisco IOS and IOS XE Software Bundled Publication
    March 2018

URL

  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr2

Revision History

  o 
    +----------+----------------------------+----------+---------+----------------+
    | Version  |        Description         | Section  | Status  |      Date      |
    +----------+----------------------------+----------+---------+----------------+
    | 1.0      | Initial public release.    | --       | Final   | 2018-March-28  |
    +----------+----------------------------+----------+---------+----------------+


======================================================

Cisco Security Advisory

Cisco IOS and IOS XE Software DHCP Version 4 Relay Denial of Service
Vulnerability

High

Advisory ID:     cisco-sa-20180328-dhcpr3

First Published: 2018 March 28 16:00 GMT

Version 1.0:     Final

Workarounds:     No workarounds available

Cisco Bug IDs:
CSCuh91645

CVE-2018-0174

CWE-20

CVSS Score:
8.6  AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X

Summary

  o A vulnerability in the DHCP option 82 encapsulation functionality of
    Cisco IOS Software and Cisco IOS XE Software could allow an
    unauthenticated, remote attacker to cause an affected device to reload,
    resulting in a denial of service (DoS) condition.

    The vulnerability exists because the affected software performs incomplete
    input validation of option 82 information that it receives in DHCP Version
    4 (DHCPv4) packets from DHCP relay agents. An attacker could exploit this
    vulnerability by sending a crafted DHCPv4 packet to an affected device. A
    successful exploit could allow the attacker to cause the affected device to
    reload, resulting in a DoS condition.

    Cisco has released software updates that address this vulnerability. There
    are no workarounds that address this vulnerability.

    This advisory is available at the following link:
    https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
    cisco-sa-20180328-dhcpr3

    This advisory is part of the March 28, 2018, release of the Cisco IOS and
    IOS XE Software Security Advisory Bundled Publication, which includes 20
    Cisco Security Advisories that describe 22 vulnerabilities. For a complete
    list of the advisories and links to them, see Cisco Event Response: March
    2018 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
    Publication.

Affected Products

  o Vulnerable Products

    This vulnerability affects Cisco devices that meet all the following
    criteria:

       The device is running a vulnerable release of Cisco IOS Software or
        Cisco IOS XE Software. For information about which Cisco IOS and IOS XE
        Software releases are vulnerable, see the Fixed Software section of
        this advisory.
       An interface of the device is configured as a DHCP relay agent.
       The device or an interface of the device is configured to insert DHCP
        relay agent information (option 82 information) into DHCP packets.
       The device or an interface of the device is configured to encapsulate
        option 82 information that it receives from other DHCP relay agents.

    Assessing the DHCP Relay Agent Configuration

    To determine whether any interfaces of a device are configured as a DHCP
    relay agent, administrators can log in to the device and use the show
    running-config | include ip helper-address command in the CLI. If the
    device is a Cisco cBR-8 Converged Broadband Router, administrators should
    instead use the show running-config | include cable helper-address command
    in the CLI.

    If the command returns output, at least one interface of the device is
    configured as a DHCP relay agent.

    The following example shows the output of the show running-config | include
    ip helper-address command for a device that is running Cisco IOS Software
    and has an interface that is configured to act as a DHCP relay agent and
    forward DHCP packets to the DHCP server address 10.10.10.1:

        Router# show running-config | include ip helper-address

        ip helper-address  10.10.10.1
        Router#

    If the show running-config | include ip helper-address command, or the show
    running-config | include cable helper-address command on a Cisco cBR-8
    Router, does not return any output, none of the interfaces of the device
    are configured as a DHCP relay agent.

    Assessing Support for Option 82 Insertion

    To determine whether a device or an interface of a device is configured to
    insert option 82 information into DHCP packets, administrators can log in
    to the device and use the show running-config | include ip dhcp relay
    information option command in the CLI.

    If the command output contains any of the following, the device is
    configured to insert option 82 information into DHCP packets:

       ip dhcp relay information option-insert--Interface configuration,
        appears under the interface that is configured as a DHCP relay agent
       ip dhcp relay information option server-id-override--Interface
        configuration, appears under the interface that is configured as a DHCP
        relay agent
       ip dhcp relay information option--Global configuration

    The following example shows the output of the show running-config | include
    ip dhcp relay information option command for a device that is running
    Cisco IOS Software and has an interface that is configured to both act as a
    DHCP relay agent and insert option 82 information into DHCP packets:

        Router# show running-config | include ip dhcp relay information option

        ip dhcp relay information option-insert
        Router#

    If the show running-config | include ip dhcp relay information option
    command does not return any output, neither the device nor any interfaces
    of the device are configured to insert option 82 information into DHCP
    packets.

    Assessing Support for Option 82 Encapsulation

    To determine whether a device or an interface of a device is configured to
    encapsulate DHCP option 82 information that it receives from other DHCP
    relay agents, administrators can log in to the device and use the show
    running-config | include ip dhcp relay information policy.* encapsulate
    command in the CLI.

    If the command output contains either of the following, the device is
    configured to encapsulate option 82 information that it receives:

       ip dhcp relay information policy-action encapsulate--Interface
        configuration, appears under the interface that is configured as a DHCP
        relay agent
       ip dhcp relay information policy encapsulate--Global configuration

    The following example shows the output of the command for a device that is
    running Cisco IOS Software and is configured to both act as a DHCP relay
    agent and encapsulate option 82 information that it receives from other
    DHCP relay agents:

        Router# show running-config | include ip dhcp relay information policy.* encapsulate

        ip dhcp relay information policy encapsulate
        Router#

    If the show running-config | include ip dhcp relay information
    policy.* encapsulate command does not return any output, neither the device
    nor any interfaces of the device are configured to encapsulate option 82
    information.

    Determining the Cisco IOS Software Release

    To determine which Cisco IOS Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS Software, the system banner displays text similar to
    Cisco Internetwork Operating System Software or Cisco IOS Software. The
    banner also displays the installed image name in parentheses, followed by
    the Cisco IOS Software release number and release name. Some Cisco devices
    do not support the show version command or may provide different output.

    The following example shows the output of the command for a device that is
    running Cisco IOS Software Release 15.5(2)T1 and has an installed image
    name of C2951-UNIVERSALK9-M:

        Router> show version

        Cisco IOS Software, C2951 Software (C2951-UNIVERSALK9-M), Version 15.5(2)T1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2015 by Cisco Systems, Inc.
        Compiled Mon 22-Jun-15 09:32 by prod_rel_team
        .
        .
        .

    For information about the naming and numbering conventions for Cisco IOS
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Determining the Cisco IOS XE Software Release

    To determine which Cisco IOS XE Software release is running on a device,
    administrators can log in to the device, use the show version command in
    the CLI, and then refer to the system banner that appears. If the device is
    running Cisco IOS XE Software, the system banner displays Cisco IOS
    Software, Cisco IOS XE Software, or similar text.

    The following example shows the output of the command for a device that is
    running Cisco IOS XE Software Release 16.2.1 and has an installed image
    name of CAT3K_CAA-UNIVERSALK9-M:

        ios-xe-device# show version

        Cisco IOS Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIVERSALK9-M), Version Denali 16.2.1, RELEASE SOFTWARE (fc1)
        Technical Support: http://www.cisco.com/techsupport
        Copyright (c) 1986-2016 by Cisco Systems, Inc.
        Compiled Sun 27-Mar-16 21:47 by mcpre
        .
        .
        .

    For information about the naming and numbering conventions for Cisco IOS XE
    Software releases, see the Cisco IOS and NX-OS Software Reference Guide.

    Products Confirmed Not Vulnerable

    No other Cisco products are currently known to be affected by this
    vulnerability.

    Cisco has confirmed that this vulnerability does not affect Cisco IOS XR
    Software or Cisco NX-OS Software.

Details

  o To exploit this vulnerability, exploit packets would need to be received
    via an interface that meets all the configuration requirements outlined in
    the Vulnerable Products section of this advisory.

Workarounds

  o There are no workarounds that address this vulnerability.

Fixed Software

  o Cisco has released free software updates that address the vulnerability
    described in this advisory. Customers may only install and expect support
    for software versions and feature sets for which they have purchased a
    license. By installing, downloading, accessing, or otherwise using such
    software upgrades, customers agree to follow the terms of the Cisco
    software license:
    https://www.cisco.com/c/en/us/products/end-user-license-agreement.html

    Additionally, customers may only download software for which they have a
    valid license, procured from Cisco directly, or through a Cisco authorized
    reseller or partner. In most cases this will be a maintenance upgrade to
    software that was previously purchased. Free security software updates do
    not entitle customers to a new software license, additional software
    feature sets, or major revision upgrades.

    When considering software upgrades, customers are advised to regularly
    consult the advisories for Cisco products, which are available from the
    Cisco Security Advisories and Alerts page, to determine exposure and a
    complete upgrade solution.

    In all cases, customers should ensure that the devices to be upgraded
    contain sufficient memory and confirm that current hardware and software
    configurations will continue to be supported properly by the new release.
    If the information is not clear, customers are advised to contact the Cisco
    Technical Assistance Center (TAC) or their contracted maintenance
    providers.

    Customers Without Service Contracts

    Customers who purchase directly from Cisco but do not hold a Cisco service
    contract and customers who make purchases through third-party vendors but
    are unsuccessful in obtaining fixed software through their point of sale
    should obtain upgrades by contacting the Cisco TAC:
    https://www.cisco.com/c/en/us/support/web/tsd-cisco-worldwide-contacts.html

    Customers should have the product serial number available and be prepared
    to provide the URL of this advisory as evidence of entitlement to a free
    upgrade.

    Cisco IOS and IOS XE Software

    To help customers determine their exposure to vulnerabilities in Cisco IOS
    and IOS XE Software, Cisco provides a tool, the Cisco IOS Software Checker,
    that identifies any Cisco Security Advisories that impact a specific
    software release and the earliest release that fixes the vulnerabilities
    described in each advisory ("First Fixed"). If applicable, the tool also
    returns the earliest release that fixes all the vulnerabilities described
    in all the advisories identified ("Combined First Fixed").

    Customers can use this tool to perform the following tasks:

       Initiate a search by choosing one or more releases from a drop-down
        list or uploading a file from a local system for the tool to parse
       Enter the output of the show version command for the tool to parse
       Create a custom search by including all previously published Cisco
        Security Advisories, a specific advisory, or all advisories in the most
        recent bundled publication

    To determine whether a release is affected by any published Cisco Security
    Advisory, use the Cisco IOS Software Checker on Cisco.com or enter a
    Cisco IOS Software or Cisco IOS XE Software release--for example, 15.1(4)M2
    or 3.13.8S--in the following field:

    [                    ] [Check]

    For a mapping of Cisco IOS XE Software releases to Cisco IOS Software
    releases, refer to the Cisco IOS XE 2 Release Notes, Cisco IOS XE 3S
    Release Notes, or Cisco IOS XE 3SG Release Notes, depending on the
    Cisco IOS XE Software release.

Exploitation and Public Announcements

  o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
    any public announcements or malicious use of the vulnerability that is
    described in this advisory.

Source

  o Cisco would like to thank Tenable for finding and reporting this
    vulnerability.

Cisco Security Vulnerability Policy

  o To learn about Cisco security vulnerability disclosure policies and
    publications, see the Security Vulnerability Policy. This document also
    contains instructions for obtaining fixed software and receiving security
    vulnerability information from Cisco.

Subscribe to Cisco Security Notifications

  o Subscribe

Related to This Advisory

  o Cisco Event Response: March 2018 Semiannual Cisco IOS and IOS XE Software
    Security Advisory Bundled Publication
    Cisco Security Blog: Cisco IOS and IOS XE Software Bundled Publication
    March 2018

URL

  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr3

Revision History

  o 
    +----------+----------------------------+----------+---------+----------------+
    | Version  |        Description         | Section  | Status  |      Date      |
    +----------+----------------------------+----------+---------+----------------+
    | 1.0      | Initial public release.    | --       | Final   | 2018-March-28  |
    +----------+----------------------------+----------+---------+----------------+

- --------------------------END INCLUDED TEXT--------------------

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