Summary

• A vulnerability in the Link Layer Discovery Protocol (LLDP) feature for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) Mode could allow an unauthenticated, adjacent attacker to cause a memory leak, which could result in an unexpected reload of the device.

  This vulnerability is due to incorrect error checking when parsing ingress LLDP packets. An attacker could exploit this vulnerability by sending a steady stream of crafted LLDP packets to an affected device. A successful exploit could allow the attacker to cause a memory leak, which could result in a denial of service (DoS) condition when the device unexpectedly reloads.

  Note: This vulnerability cannot be exploited by transit traffic through the device. The crafted LLDP packet must be targeted to a directly connected interface, and the attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent). In addition, the attack surface for this vulnerability can be reduced by disabling LLDP on interfaces where it is not required.

  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-aci-lldp-dos-ySCNZOpX

  This advisory is part of the February 2023 Cisco FXOS and NX-OS Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: February 2023 Semiannual Cisco FXOS and NX-OS Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects Cisco Nexus 9000 Series Fabric Switches in ACI Mode if they are running a vulnerable release of Cisco NX-OS Software and have the LLDP feature enabled.

  For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.

  Determine Whether LLDP is Enabled

  To determine the LLDP status of a Cisco Nexus 9000 Series Fabric Switch in ACI Mode, use the show lldp interface ethernet port/interface command. If the transmit (tx) and receive (rx) statuses are Y, LLDP is enabled on the interface, as in the following example:

  #show lldp interface ethernet port/interface
  Interface Information:Enable (tx/rx/dcbx): Y/Y/N    Port Mac address: 00:fe:c8:09:e2:92

  
  

  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:

  • Firepower 1000 Series
  • Firepower 2100 Series
  • Firepower 4100 Series
  • Firepower 9300 Security Appliances
  • MDS 9000 Series Multilayer Switches
  • Nexus 1000 Virtual Edge for VMware vSphere
  • Nexus 1000V Switch for Microsoft Hyper-V
  • Nexus 1000V Switch for VMware vSphere
  • Nexus 3000 Series Switches
  • Nexus 5500 Platform Switches
  • Nexus 5600 Platform Switches
  • Nexus 6000 Series Switches
  • Nexus 7000 Series Switches
  • Nexus 9000 Series Switches in standalone NX-OS mode
  • Secure Firewall 3100 Series
  • UCS 6200 Series Fabric Interconnects
  • UCS 6300 Series Fabric Interconnects
  • UCS 6400 Series Fabric Interconnects
  • UCS 6500 Series Fabric Interconnects

Indicators of Compromise

• An exploit of this vulnerability can result in a memory leak in the LLDP process, which could cause a crash of the device once there is insufficient system memory available.

  To monitor memory usage of the LLDP process, use the ps aux --sort -rss CLI command or the ps aux --sort -rss | grep lldp CLI command. In the output, the VSZ column indicates the total amount of memory in use by the LLDP process. If this number slowly increases over time and never decreases, this could be an indication that this vulnerability is being exploited. A device reboot is required to reclaim the memory.

  leaf# ps aux --sort -rss
  USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  root     24764  2.1  3.3 2454992 544656 ?      Ssl  Jan29 3772:19 /isan/bin/coop
  root     24769  0.8  2.8 2150308 458840 ?      Ssl  Jan29 1497:31 /isan/bin/routing-sw/isis -t isis_infra
  root     22160  0.0  2.8 1966352 454464 ?      Ssl  Jan29  71:52 /isan/bin/nfm
  root     56391  0.0  2.7 1963948 451276 ?      Ss   Jan29   5:49 /isan/bin/cts -t
  root     24763  0.0  2.4 1918348 394152 ?      Ssl  Jan29   6:27 /isan/bin/dhcp_snoop
  root     22222  0.0  2.3 1111704 379436 ?      Ssl  Jan29  67:56 /isan/bin/acllog
  root     24754  0.0  2.3 1895068 378796 ?      Ss   Jan29  52:41 /isan/bin/oam
  root     24757  0.0  2.3 4190440 376808 ?      Ss   Jan29 134:20 /isan/bin/lldp
  
  leaf#ps aux --sort -rss | grep lldp
  root     24757  0.0  2.3 4190440 376808 ?      Ss   Jan29 134:20 /isan/bin/lldp

Workarounds

• There are no workarounds that address this vulnerability.

  However, if LLDP is not enabled on an interface, this vulnerability cannot be exploited on that interface. As a mitigation, disable LLDP on all interfaces where it is not required. Use the CLI commands no lldp transmit and no lldp receive. For additional information, see Cisco APIC Layer 2 Networking Configuration Guide.

  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

• 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 NX-OS Software

  To help customers determine their exposure to vulnerabilities in Cisco NX-OS 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 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 search for vulnerabilities that affect a specific software release. 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. Choose the appropriate software.
  3. Choose the appropriate platform.
  4. Enter a release number-for example, 7.0(3)I7(5) for Cisco Nexus 3000 Series Switches or 14.0(1h) for Cisco NX-OS Software in ACI mode.
  5. Click Check.

  
  

  Only this advisory All Critical and High advisories All advisories Cisco NX-OS Software Cisco NX-OS Software in ACI Mode Any Platform MDS 9000 Series Multilayer Switches Nexus 1000V Series Switches Nexus 3000 Series Switches Nexus 5000 Series Switches Nexus 6000 Series Switches Nexus 7000 Series Switches Nexus 9000 Series Switches

  
  

  Additional Resources

  For help determining the best Cisco NX-OS Software release for a Cisco Nexus Switch, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco MDS Series Switches
  Cisco Nexus 1000V for VMware Switch
  Cisco Nexus 3000 Series Switches
  Cisco Nexus 5500 Platform Switches
  Cisco Nexus 5600 Platform Switches
  Cisco Nexus 6000 Series Switches
  Cisco Nexus 7000 Series Switches
  Cisco Nexus 9000 Series Switches
  Cisco Nexus 9000 Series ACI-Mode Switches

  To determine the best release for Cisco UCS Software, see the Recommended Releases documents in the release notes for the device.

Exploitation and Public Announcements

• 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

• 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-aci-lldp-dos-ySCNZOpX

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2023-FEB-22

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