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