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AUSCERT External Security Bulletin Redistribution
ESB-2023.1730
Cisco IOS and IOS XE Software IPv6 DHCP (DHCPv6) Relay and
Server Denial of Service Vulnerability
23 March 2023
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS and IOS XE Software IPv6 DHCP (DHCPv6) Relay and Server
Publisher: Cisco Systems
Operating System: Cisco
Resolution: Patch/Upgrade
CVE Names: CVE-2023-20080
Original Bulletin:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-dhcpv6-dos-44cMvdDK
Comment: CVSS (Max): 8.6 CVE-2023-20080 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
CVSS Source: Cisco Systems
Calculator: https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
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Cisco IOS and IOS XE Software IPv6 DHCP (DHCPv6) Relay and Server Denial of
Service Vulnerability
Priority: High
Advisory ID: cisco-sa-ios-dhcpv6-dos-44cMvdDK
First Published: 2023 March 22 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvw60355
CVE Names: CVE-2023-20080
Summary
o A vulnerability in the IPv6 DHCP version 6 (DHCPv6) relay and server
features of Cisco IOS and IOS XE Software could allow an unauthenticated,
remote attacker to trigger a denial of service (DoS) condition.
This vulnerability is due to insufficient validation of data boundaries. An
attacker could exploit this vulnerability by sending crafted DHCPv6
messages to an affected device. A successful exploit could allow the
attacker to cause the device to reload unexpectedly.
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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-dhcpv6-dos-44cMvdDK
This advisory is part of the March 2023 release of the Cisco IOS and IOS XE
Software Security Advisory Bundled Publication. For a complete list of the
advisories and links to them, see Cisco Event Response: March 2023
Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled
Publication .
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices if they are running a vulnerable
release of Cisco IOS or IOS XE Software and have IPv6 and the DHCPv6 relay
or server feature enabled. IPv6 and DHCPv6 are disabled in Cisco IOS and
IOS XE Software by default.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine the Device Configuration
To determine whether a device is enabled to process IPv6 traffic or whether
a device has the DHCPv6 relay or server feature enabled, use the
instructions below.
Determine the IPv6 Configuration
For a device to process IPv6 traffic, both of the following conditions need
to be met:
IPv6 unicast routing is enabled globally.
At least one interface has an IPv6 address configured.
To determine the IPv6 configuration, use the show running-config CLI
command. The following example shows the output on a device that has IPv6
unicast routing enabled globally and that has IPv6 address 2001:DB8:1:40::1
/64 configured on interface GigabitEthernet1 :
router#show running-config
.
.
.
ipv6 unicast-routing
.
.
.
interface GigabitEthernet1
.
.
.
ipv6 address 2001:DB8:1:40::1/64
.
.
.
If either of the following is true, the device is not affected by this
vulnerability:
IPv6 traffic processing is not enabled using the ipv6 unicast-routing
configuration command.
No interface has an IPv6 address configured using the ipv6 address
configuration command.
Determine the DHCPv6 Relay Configuration
To determine whether the DHCPv6 relay feature is enabled, use the show
running-config | include ipv6 dhcp relay CLI command. The following example
shows the output on a device that has the DHCPv6 relay feature enabled
under one interface:
router#show running-config | include ipv6 dhcp relay
ipv6 dhcp relay destination 2001:DB8:2:40::10
If this command returns empty output, the DHCPv6 relay feature is not
enabled.
Determine the DHCPv6 Server Configuration
When both of the following conditions are met, the DHCPv6 server feature is
enabled:
A DHCPv6 address pool is configured globally.
The DHCPv6 server feature is enabled on at least one interface and
points to an existing DHCPv6 pool.
To determine whether the DHCPv6 server feature is enabled, use the show
running-config CLI command. The following example shows the output on a
device that has DHCPv6 pool DHCPv6_POOL configured globally and the DHCPv6
server feature enabled under interface GigabitEthernet1 :
router#show running-config
.
.
.
ipv6 dhcp pool DHCPv6_POOL
.
.
.
interface GigabitEthernet1
.
.
.
ipv6 dhcp server DHCPv6_POOL
.
.
.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Cisco has confirmed that this vulnerability does not affect the following
Cisco products:
Adaptive Security Appliance (ASA) Software
Firepower Management Center (FMC) Software
Firepower Threat Defense (FTD) Software
FXOS Software
IOS XR Software
Meraki products
Next-Generation Intrusion Prevention System (NGIPS) Software
NX-OS Software
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 with service contracts that entitle
them to regular software updates should obtain security fixes through their
usual update channels.
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.
The Cisco Support and Downloads page on Cisco.com provides information
about licensing and downloads. This page can also display customer device
support coverage for customers who use the My Devices tool.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories 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 the Cisco Software Checker . This tool
identifies any Cisco security advisories that impact a specific software
release and the earliest release that fixes the vulnerabilities that are
described in each advisory ("First Fixed"). If applicable, the tool also
returns the earliest release that fixes all the vulnerabilities that are
described in all the advisories that the Software Checker identifies
("Combined First Fixed").
To use the tool, go to the Cisco Software Checker page and follow the
instructions. Alternatively, use the following form to determine whether a
release is affected by any Cisco Security Advisory. To use the form, follow
these steps:
1. Choose which advisories the tool will search-only this advisory, only
advisories with a Critical or High Security Impact Rating (SIR) , or
all advisories.
2. Enter a release number-for example, 15.9(3)M2 or 17.3.3.
3. Click Check .
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 This vulnerability was found during the resolution of a Cisco TAC support
case.
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 2023 Semiannual Cisco IOS and IOS XE Software
Security Advisory Bundled Publication
URL
o https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ios-dhcpv6-dos-44cMvdDK
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2023-MAR-22 |
+----------+---------------------------+----------+--------+--------------+
Legal Disclaimer
o THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND
OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT
OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES
THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information
or contain factual errors. The information in this document is intended for
end users of Cisco products.
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