Summary

• A vulnerability in ICMPv6 inspection when configured with the Snort 2 detection engine for Cisco Firepower Threat Defense (FTD) Software or Cisco FirePOWER Services could allow an unauthenticated, remote attacker to cause the CPU of an affected device to spike to 100 percent, which could stop all traffic processing and result in a denial of service (DoS) condition. FTD management traffic is not affected by this vulnerability.

  This vulnerability is due to improper error checking when parsing fields within the ICMPv6 header. An attacker could exploit this vulnerability by sending a crafted ICMPv6 packet through an affected device. A successful exploit could allow the attacker to cause the device to exhaust CPU resources and stop processing traffic, resulting in a DoS condition.

  Note: To recover from the DoS condition, the Snort 2 Detection Engine, the Cisco FTD device, or the Cisco FirePOWER Services device may need to be restarted. For more information, see the Details section of this advisory.

  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-ftd-icmpv6-dos-4eMkLuN

  This advisory is part of the November 2023 release of the Cisco ASA, FTD, and FMC Security Advisory Bundled publication. For a complete list of the advisories and links to them, see Cisco Event Response: November 2023 Semiannual Cisco ASA, FMC, and FTD Software Security Advisory Bundled Publication.

Affected Products

• Vulnerable Products

  This vulnerability affects the following Cisco products if they were running a vulnerable release of Cisco software and were configured with a network discovery policy that enables both host and application detection and invokes the Snort 2 Detection Engine:

  • FirePOWER Services - All platforms
  • Firepower Threat Defense (FTD) Software - All platforms

  By default, the network discovery policy is configured for application detection only. For this vulnerability to be exploited, Snort 2 must be active.

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

  Determine the Network Discovery Policy Configuration

  To determine whether the network discovery policy is configured for host and application detection, choose Policies > Network Discovery and review the document Host and Application Detection Fundamentals.

  Determine the Snort 2 Status

  To determine whether Snort 2 is running, see Determine the Active Snort Version that Runs on Firepower Threat Defense (FTD).

  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
  • Open Source Snort 2
  • Open Source Snort 3

Details

• Exploitation of this vulnerability can cause the Snort 2 Detection Engine to exhaust CPU resources. There are two ways to recover from the DoS condition:

  • Restart the Cisco FTD or Cisco FirePOWER Services device.
  • Restart the Snort 2 Detection Engine.

  Restart the Snort 2 Detection Engine

  To restart the Snort 2 Detection Engine, use the expert mode CLI command pmtool RestartByType de, as shown in the following example:

  > expert 
  admin@ftd:/ngfw/Volume/home/admin$ pmtool RestartByType de 

  This is a disruptive action, so Cisco recommends determining if exploitation is occurring before restarting. For further assistance, contact the Cisco Technical Assistance Center (TAC).

Indicators of Compromise

• Exploitation of this vulnerability can exhaust CPU resources.

  Check for High CPU Usage of the Snort 2 Detection Engine

  If the Cisco FTD or Cisco FirePOWER Services device is managed by Cisco FMC or Cisco Firepower Device Management (FDM), the management station may alert about the high CPU usage. To monitor CPU usage, use the expert mode CLI command top, as shown in the following example:

  > expert 
  admin@ftd:/ngfw/Volume/home/admin$ top -p `pidof snort | sed -e "s/ /,/g"`
  top - 08:03:28 up 6 days, 23:21,  2 users,  load average: 4.20, 3.19, 3.06 
  Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie 
  %Cpu(s): 99.7 us, 1.6 sy, 0.1 ni, 62.6 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st 
  MiB Mem :   7899.7 total,   1483.3 free,   5743.5 used,    672.9 buff/cache
  MiB Swap:   9461.2 total,   8276.2 free,   1185.0 used.   1517.3 avail Mem
  
  PID       USER    PR   NI    VIRT         RES          SHR      S   %CPU   %MEM     TIME+       COMMAND
  59156     root    1    -19   3359960      868608       35488    R   99.7  10.7     35:08.57    snort

  Note: There can be one or more Snort instances that are active on a Cisco FTD or a Cisco FirePOWER Services device.

Workarounds

• There are no workarounds that address this vulnerability.

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 ASA, FMC, and FTD Software

  To help customers determine their exposure to vulnerabilities in Cisco ASA, FMC, and FTD 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 search for vulnerabilities that affect a specific software release. To use the form, follow these steps:

  1. Choose which advisories the tool will search-all advisories, only advisories with a Critical or High Security Impact Rating (SIR), or only this advisory.
  2. Choose the appropriate software.
  3. Choose the appropriate platform.
  4. Enter a release number-for example, 9.16.2.11 for Cisco ASA Software or 6.6.7 for Cisco FTD Software.
  5. Click Check.

  Only this advisory All Critical and High advisories All advisories Cisco ASA Software Cisco FMC Software Cisco FTD Software Any Platform 3000 Series Industrial Security Appliances (ISA) ASA 5500-X Series Firewalls ASA Service Module Adaptive Security Virtual Appliance (ASAv) Firepower 1000 Series Firepower 2100 Series Firepower 4100 Series Firepower 9000 Series Secure Firewall 3100 Series

  
  

  For instructions on upgrading your FTD device, see Cisco Firepower Management Center Upgrade Guide.

  
  

  Additional Resources

  For help determining the best Cisco ASA, FTD, or FMC Software release, see the following Recommended Releases documents. If a security advisory recommends a later release, Cisco recommends following the advisory guidance.

  Cisco ASA Compatibility
  Cisco Secure Firewall ASA Upgrade Guide
  Cisco Secure Firewall Threat Defense Compatibility Guide

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 by Sanmith Prakash of Cisco during internal security testing.

URL

• https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-icmpv6-dos-4eMkLuN

Revision History

• Version	Description	Section	Status	Date
  1.1	Updated to include Cisco FirePOWER Services as vulnerable.	Summary, Vulnerable Products, Details, Indicators of Compromise	Final	2023-NOV-16
  1.0	Initial public release.	-	Final	2023-NOV-01

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