Cisco IOS contains a flaw that may allow a malicious user to bypass Access Control Lists. The issue is triggered by a combination of configuration options which combine to affect the way certain ACLs are evaluated. It is possible that the flaw may allow unauthorized network traffic resulting in a loss of confidentiality, integrity, and/or availability.
Upgrade to version recommended by Cisco product matrix, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.