Cisco IOS 15.2(04)M6 and 15.4(03)S lets physical-interface ACLs supersede tunnel-interface ACLs, which allows remote attackers to bypass intended network-traffic restrictions in opportunistic circumstances by using a tunnel, aka Bug ID CSCur01042.
http://www.securitytracker.com/id/1034141
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151112-ios2