Summary

• A vulnerability in the TL1 function of Cisco Network Convergence System (NCS) 4000 Series could allow an authenticated, local attacker to cause a memory leak in the TL1 process.

  This vulnerability is due to TL1 not freeing memory under some conditions. An attacker could exploit this vulnerability by connecting to the device and issuing TL1 commands after being authenticated. A successful exploit could allow the attacker to cause the TL1 process to consume large amounts of memory. When the memory reaches a threshold, the Resource Monitor (Resmon) process will begin to restart or shutdown the top five consumers of memory, resulting in a denial of service (DoS).

  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-ncs4k-tl1-GNnLwC6

  This advisory is part of the September 2022 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2022 Semiannual Cisco IOS XR Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected Cisco NCS 4000 Series devices if they were running a vulnerable release of Cisco IOS XR Software.

  For information about which Cisco software releases were vulnerable at the time of publication, see the Fixed Software section of this advisory. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  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 Cisco IOS XE Software on Cisco NCS 4200 Series devices.

Workarounds

• There are no workarounds that address this vulnerability. However, administrators can monitor the memory that is held by the TL1 process and restart it if it reaches about 400MB. To obtain the current TL1 memory holdings, issue the show processes memory command. If memory exceeds 400MB, restart the TL1 process, as shown in the following example:

  RP/0/RP0:NCS4000#show processes memory | include tl1 
  Tue Sep 06 18:52:49.658 EST
  175 532 624248 212 299563 tl1
  152 244  77696 136   3439 tl1_parser 
  RP/0/RP0:NCS4000#
  RP/0/RP0:NCS4000#process restart tl1

  While this mitigation has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.

Fixed Software

• 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.

  Fixed Releases

  At the time of publication, the release information in the following table(s) was accurate. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  The left column lists Cisco software releases, and the right column indicates whether a release was affected by the vulnerability that is described in this advisory and which release included the fix for this vulnerability.

  Cisco IOS XR Software Release	First Fixed Release
  Earlier than 6.5.32	6.5.32

  At the time of publication, Cisco had released the following SMUs to address this vulnerability. See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information, including SMU availability. Customers who require SMUs for platforms or releases that are not listed are advised to contact their support organization.

  Cisco IOS XR Software Release	SMU Name
  6.5.26	ncs4k-6.5.26.CSCwb16005

  The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.

Exploitation and Public Announcements

• The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

Source

• This vulnerability was found during the resolution of a Cisco TAC support case.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ncs4k-tl1-GNnLwC6

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2022-SEP-14

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