A vulnerability in the configured security policies, including drop email filtering, in Cisco AsyncOS for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass a configured drop filter by using an email with a corrupted attachment. More Information: CSCuz01651. Known Affected Releases: 10.0.9-015 9.7.1-066 9.9.6-026.
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161026-esa5