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AUSCERT External Security Bulletin Redistribution
ESB-2019.0083
Cisco IOS and IOS XE Software TCP Denial of Service Vulnerability
10 January 2019
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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-2018-0282
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190109-tcp
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS and IOS XE Software TCP Denial of Service Vulnerability
Importance: Medium
Advisory ID: cisco-sa-20190109-tcp
First Published: 2019 January 9 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvg39082
CVE-2018-0282
CWE-371
CVSS Score: Base 6.8
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X
Summary
o A vulnerability in the TCP socket code of Cisco IOS and IOS XE Software
could allow an unauthenticated, remote attacker to cause an affected device
to reload. The vulnerability is due to a state condition between the socket
state and the transmission control block (TCB) state. While this
vulnerability potentially affects all TCP applications, the only affected
application observed so far is the HTTP server.
An attacker could exploit this vulnerability by sending specific HTTP
requests at a sustained rate to a reachable IP address of the affected
software. A successful exploit could allow the attacker to cause the
affected device to reload, resulting in a denial of service (DoS) condition
on an affected device.
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-20190109-tcp
Affected Products
o Vulnerable Products
This vulnerability affects Cisco devices that are running a vulnerable
release of Cisco IOS or IOS XE Software if the HTTP Server feature is
enabled. The default state of the HTTP Server feature is version-dependent.
For information about which software releases are vulnerable, see the Fixed
Software section of this advisory.
Assessing the HTTP Server Configuration
To determine whether the HTTP Server feature is enabled for a device,
administrators can log in to the device and use the show running-config |
include http (secure|server) command in the CLI to check for the presence
of the ip http server command or the ip http secure-server command in the
global configuration. If either command is present and configured, the HTTP
Server feature is enabled for the device.
The following example shows the output of the show running-config | include
http (secure|server) command for a router that has the HTTP Server feature
enabled:
Router# show running-config | include http (secure|server)
ip http server
ip http secure-server
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
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by this vulnerability.
Details
o For this vulnerability to be exploited, a large number of TCP sessions
would have to be set up/torn down to the affected device. Controlling HTTP/
HTTPS access to the device will limit the likelihood of an exploit of this
vulnerability.
Indicators of Compromise
o Prior to the crash, a message similar to the following will appear,
indicating an issue with the HTTP CORE process:
%TCP-2-INVALIDTCB: Invalid TCB pointer: 0x3CBC2DF0 -Process= "HTTP CORE", ipl= 0, pid= 334
Workarounds
o There are no workarounds that address this vulnerability.
Administrators who do not use the web UI can mitigate this vulnerability by
disabling the HTTP Server feature on an affected device. To disable the
feature, use the no ip http server and no ip http secure-server commands in
the CLI.
Limiting access to the HTTP server to trusted networks will limit exposure
to this vulnerability. The following example shows how to allow remote
access to the HTTP server from the trusted 192.168.0.0/24 network:
!
ip http access-class 75
ip http secure-server
!
access-list 75 permit 192.168.0.0 0.0.0.255
access-list 75 deny any
!
Note: In newer versions of Cisco IOS and IOS XE Software, to apply the
access list use the ip http access-class ipv4 75 command for the previous
example.
Fixed Software
o For information about fixed software releases, consult the Cisco bug ID(s)
at the top of this advisory.
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.
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]
By default, the Cisco IOS Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, use the Cisco IOS
Software Checker on Cisco.com and check the Medium check box in the Impact
Rating drop-down list.
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 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.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-20190109-tcp
Revision History
o
+----------+---------------------------+----------+--------+------------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+------------------+
| 1.0 | Initial public release. | -- | Final | 2019-January-09 |
+----------+---------------------------+----------+--------+------------------+
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