Cisco IOS Software Virtual PPP Interfaces Security Bypass Vulnerability

Summary

• A vulnerability in Cisco devices that are running Cisco IOS Software Release 15.2(04)M or Cisco IOS Software Release 15.4(03)M and are configured to use access control lists (ACLs) could allow a user who is connected to an authenticated PPP session to bypass ACLs that are configured on virtual PPP interfaces, if the ACL on the physical interface permits the traffic to pass.
  
  The vulnerability is due to the physical interface ignoring virtual PPP ACLs. An attacker could exploit this vulnerability to bypass virtual PPP ACLs and pass denied traffic across virtual PPP interfaces. A successful exploit could allow the attacker to pass traffic as if the ACLs do 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-ios1

Affected Products

• Vulnerable Products

  Cisco IOS Software Release 15.2(04)M and Cisco IOS Software Release 15.4(03)M.

  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 the ACLs on the virtual PPP interfaces do not appear to deny traffic that is permitted to pass on the physical interfaces.

Workarounds

• There are no workarounds that mitigate this vulnerability.

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 upgrade 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-ios1

Revision History

• Version	Description	Section	Status	Date
  1.0	Initial public release.	-	Final	2015-November-13

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