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AUSCERT External Security Bulletin Redistribution
ESB-2020.3301
Cisco IOS XE Software IP Service Level Agreements Denial of
Service Vulnerability
25 September 2020
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco IOS XE Software
Publisher: Cisco Systems
Operating System: Cisco
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-3422
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ipsla-jw2DJmSv
- --------------------------BEGIN INCLUDED TEXT--------------------
Cisco IOS XE Software IP Service Level Agreements Denial of Service
Vulnerability
Priority: High
Advisory ID: cisco-sa-ipsla-jw2DJmSv
First Published: 2020 September 24 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds availableCisco Bug IDs: CSCvs19635
CVE-2020-3422
CWE-371
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 IP Service Level Agreement (SLA) responder feature
of Cisco IOS XE Software could allow an unauthenticated, remote attacker to
cause the IP SLA responder to reuse an existing port, resulting in a denial
of service (DoS) condition.
The vulnerability exists because the IP SLA responder could consume a port
that could be used by another feature. An attacker could exploit this
vulnerability by sending specific IP SLA control packets to the IP SLA
responder on an affected device. The control packets must include the port
number that could be used by another configured feature. A successful
exploit could allow the attacker to cause an in-use port to be consumed by
the IP SLA responder, impacting the feature that was using the port and
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-ipsla-jw2DJmSv
This advisory is part of the September 24, 2020, release of the Cisco IOS
and IOS XE Software Security Advisory Bundled Publication, which includes
25 Cisco Security Advisories that describe 34 vulnerabilities. For a
complete list of the advisories and links to them, see Cisco Event
Response: September 2020 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 XE Software and have the IP SLA responder feature
enabled without additional parameters.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Determine the Device Configuration
To determine whether the IP SLA responder feature is enabled for a device,
log in to the device and use the show running-config | include ip sla
responder command in the CLI. If the ip sla responder command is present in
the global configuration, the IP SLA responder feature is enabled for the
device, as shown in the following example:
Router# show running-config | include ip sla responder
ip sla responder
Router#
Note: If each ip sla responder command is followed by additional
parameters, the device is not affected by this vulnerability.
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:
IOS Software
IOS XR Software
NX-OS Software
Workarounds
o There are no workarounds that address this vulnerability.
To mitigate the attack vector from unauthenticated attackers, ensure that
the IP SLA responder has a password associated with it. To enable
authentication on the IP SLA responder, see the following example:
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#key chain <1>
Router(config-keychain)#key <1>
Router(config-keychain-key)#key-string <example>
Router(config-keychain-key)#exit
Router(config-keychain)#exit
Router(config)#ip sla key
Router(config)#ip sla key-chain <1>
Router(config)#^Z
Router#
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 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 to identify
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 the Cisco Software Checker to search advisories in the
following ways:
Choose the software and one or more releases
Upload a .txt file that includes a list of specific releases
Enter the output of the show version command
After initiating a search, customers can customize the search to include
all Cisco Security Advisories, a specific advisory, or all advisories in
the most recent bundled publication.
Customers can also use the following form to determine whether a release is
affected by any Cisco Security Advisory by entering a Cisco IOS or IOS XE
Software release-for example, 15.1(4)M2 or 3.13.8S :
[ ] [Check]
By default, the Cisco Software Checker includes results only for
vulnerabilities that have a Critical or High Security Impact Rating (SIR).
To include results for Medium SIR vulnerabilities, customers can use the
Cisco Software Checker on Cisco.com and check the Medium check box in the
drop-down list under Impact Rating when customizing a search.
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.
Related to This Advisory
o Cisco Event Response: September 2020 Semiannual Cisco IOS and IOS XE
Software Security Advisory Bundled Publication
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/
cisco-sa-ipsla-jw2DJmSv
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2020-SEP-24 |
+----------+---------------------------+----------+--------+--------------+
- --------------------------END INCLUDED TEXT--------------------
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