Summary

• A vulnerability in Cisco Unified Threat Defense (UTD) Snort Intrusion Prevention System (IPS) Engine for Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass configured security policies or cause a denial of service (DoS) condition on an affected device.

  This vulnerability is due to insufficient validation of HTTP requests when they are processed by Cisco UTD Snort IPS Engine. An attacker could exploit this vulnerability by sending a crafted HTTP request through an affected device. A successful exploit could allow the attacker to trigger a reload of the Snort process. If the action in case of Cisco UTD Snort IPS Engine failure is set to the default, fail-open, successful exploitation of this vulnerability could allow the attacker to bypass configured security policies. If the action in case of Cisco UTD Snort IPS Engine failure is set to fail-close, successful exploitation of this vulnerability could cause traffic that is configured to be inspected by Cisco UTD Snort IPS Engine to be dropped.

  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-utd-snort3-dos-bypas-b4OUEwxD

Affected Products

• Vulnerable Products

  At the time of publication, this vulnerability affected the following Cisco products if they were running a vulnerable release of Cisco UTD Snort IPS Engine for Cisco IOS XE Software and had the Web Filtering feature, the Multi-Tenancy feature, or both enabled:

  • 1000 Series Integrated Services Routers (ISRs)
  • 4000 Series ISRs
  • Catalyst 8000V Edge Software
  • Catalyst 8200 Series Edge Platforms
  • Catalyst 8300 Series Edge Platforms
  • Catalyst 8500L Series Edge Platforms
  • Catalyst IR8300 Rugged Series Routers

  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.

  Determine the Device Configuration

  For information about how to determine the device configuration, see the following sections.

  Determine Whether Cisco UTD Snort IPS Engine Is Enabled

  To determine whether Cisco UTD Snort IPS Engine is enabled on a device, use the show utd engine standard status command on the device CLI. If there is no output, Cisco UTD Snort IPS Engine is not enabled, and the device is not affected by this vulnerability. If the output shows Yes under Running, Cisco UTD Snort IPS Engine is enabled and the device is affected, as shown in the following example:

  Router#show utd engine standard status 
  
  Profile              : Cloud-Low
  System memory        :
               Usage  : 6.00 %
               Status : Green
  Number of engines    : 1
  
  
  Engine        Running    Health     Reason    
  =======================================================
  Engine(#1):   Yes        Green      None
  =======================================================
  .
  .
  .

  Determine Whether Multi-Tenancy Is Enabled

  To determine whether Multi-Tenancy is enabled on Cisco UTD Snort IPS Engine, use the show utd engine standard config | include Multi-tenancy command on the device CLI. If there is no output, Multi-Tenancy is disabled, and the device is affected by this vulnerability only if Web Filtering is enabled. If the output shows Enabled under Multi-tenancy, Multi-Tenancy is enabled, and the device is affected regardless of the Web Filtering configuration, as shown in the following example:

  Router#show utd engine standard config | include Multi-tenancy
  Multi-tenancy: Enabled

  Determine Whether Web Filtering Is Enabled

  To determine whether Web Filtering is enabled on Cisco UTD Snort IPS Engine, use the show utd engine standard config | include Web-Filter command on the device CLI. If the output shows Disabled or there is no output, Web Filtering is disabled, and the device is affected by this vulnerability only if Multi-Tenancy is enabled. If the output shows Enabled under Web-Filter, Web Filtering is enabled, and the device is affected regardless of the Multi-Tenancy configuration, as shown in the following example:

  Router#show utd engine standard config | include Web-Filter
  Web-Filter    : Enabled
  

  Determine the Configured Fail Policy

  To determine the configured action in case of Cisco UTD Snort IPS Engine failure, use the show platform software utd global | include Fail Policy command on the device CLI. The following example shows the output of the show platform software utd global | include Fail Policy command on a device that has the action in case of Cisco UTD Snort IPS Engine failure set to Fail-open:

  Router# show platform software utd global | include Fail Policy
  Fail Policy          : Fail-open
  

  
  

  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 products:

  • Cisco Adaptive Security Appliance (ASA) Software
  • Cisco Catalyst 8500 Series Edge Platforms
  • Cisco Cloud Services Routers 1000V
  • Cisco Firepower Threat Defense (FTD) Software
  • Cisco Integrated Services Virtual Routers (ISRv)
  • Cisco Secure Firewall Management Center (FMC) Software, formerly Firepower Management Center Software
  • Open Source Snort

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, the release information in the following table 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 UTD Snort IPS Engine Release	First Fixed Release
  Earlier than 17.12	Not vulnerable.
  17.12	17.12.4
  17.13	Migrate to a fixed release.
  17.14	Not vulnerable.

  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-utd-snort3-dos-bypas-b4OUEwxD

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2024-SEP-25

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