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