Summary

• Multiple Cisco products are affected by a vulnerability in the Snort application detection engine that could allow an unauthenticated, remote attacker to bypass the configured policies on an affected system.

  The vulnerability is due to a flaw in the detection algorithm. An attacker could exploit this vulnerability by sending crafted packets that would flow through an affected system. A successful exploit could allow the attacker to bypass the configured policies and deliver a malicious payload to the protected network.

  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-snort-app-bypass-cSBYCATq

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected all open source Snort project releases earlier than Release 2.9.14. For more information, see the Snort website.

  At the time of publication, this vulnerability affected the following Cisco products if they were running a vulnerable release of Cisco software:

  • 3000 Series Industrial Security Appliances (ISAs)
  • Firepower Threat Defense (FTD) Software

  At the time of publication, this vulnerability affected the following Cisco products if they were running a release earlier than the first fixed release of Cisco Unified Threat Defense (UTD) Snort Intrusion Prevention System (IPS) Engine for Cisco IOS XE Software or Cisco UTD Engine for Cisco IOS XE SD-WAN Software. Note: UTD is not installed on these devices by default. If the UTD file is not installed, the device is not vulnerable.

  • 1000 Series Integrated Services Routers (ISRs)
  • 4000 Series Integrated Services Routers (ISRs)
  • Cloud Services Router 1000V
  • Integrated Services Virtual Router (ISRv)

  For information about which Cisco software releases are vulnerable, 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.

  Determine Whether UTD is Enabled

  To determine whether UTD is enabled on a device, issue the show utd engine standard status command and check for a Yes under Running. If there is no output, the device is not affected. The following output example shows a device that has UTD enabled:

  Router# show utd engine standard status 
  Engine version       : 1.0.19_SV2.9.16.1_XE17.3
  Profile              : Cloud-Low
  System memory        :
               Usage  : 6.00 %
               Status : Green
  Number of engines    : 1

  
  

  Engine        Running    Health     Reason    
  ===========================================
  Engine(#1):   Yes        Green      None
  =======================================================
  
  .
  .
  .

  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
  • Meraki Security Appliances

Workarounds

• There are no workarounds that address this vulnerability.

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, Cisco Firepower Threat Defense (FTD) releases 6.5.0.5 and later contained the fix for this vulnerability.

  At the time of publication, Cisco UTD Snort IPS Engine Software for IOS XE 17.4.1¹ contained the fix for this vulnerability.

  At the time of publication, the open source Snort project release 2.9.14.10 and later contained the fix for this vulnerability. For more information, see the Snort website.

  See the Details section in the bug ID(s) at the top of this advisory for the most complete and current information.

  1. Starting in 17.2.1, IOS XE and IOS XE SD-WAN use the same image file.

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-snort-app-bypass-cSBYCATq

Revision History

• Version	Description	Section	Status	Date
  1.2	Added instructions to determine whether UTD is enabled and running.	Vulnerable Products	Final	2022-MAY-16
  1.1	Updated vulnerability information for Cisco UTD Engine requirements.	Vulnerable Products	Final	2021-NOV-12
  1.0	Initial public release.	—	Final	2021-JAN-13

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