Cisco IOS Software Tunnel Interfaces Security Bypass Vulnerability

Summary

• A vulnerability in Cisco devices running IOS Software versions 15.2(04)M6 and 15.4(03)S configured with access control lists (ACLs) could allow an unauthenticated, remote user connected to a tunnel interface to bypass configured ACLs on tunnel interfaces if the ACL on the physical interface permits the traffic to pass.
  
  The vulnerability is due to the physical interface ignoring the tunnel interface ACLs. A user could exploit this vulnerability to bypass configured tunnel interface ACLs and pass denied traffic across tunnel interfaces. If successful, the user could pass traffic as if the ACLs did not exist.
  
  Cisco has released software updates that address this vulnerability. Workarounds that mitigate this vulnerability are not available.
  
  This advisory is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151112-ios2

Affected Products

• Vulnerable Products

  Cisco IOS Software versions 15.2(04)M6 and 15.4(03)S.

  Products Confirmed Not Vulnerable

  No other Cisco products are currently known to be affected by this vulnerability.

Indicators of Compromise

• A device may indicate compromise if ACLs on tunnel interfaces do not appear to deny traffic that is allowed on the physical interfaces.

Workarounds

• Workarounds are not available.

Fixed Software

• When considering software upgrades, customers are advised to consult the Cisco Security Advisories and Responses archive at http://www.cisco.com/go/psirt and review subsequent advisories 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.
  
  

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.

URL

• http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151112-ios2

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release	-	Final	2015-November-12

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