Cisco Email Security Appliance Attachment Filter Bypass Vulnerability

A vulnerability in the email message scanning of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass configured filters on the device.

The vulnerability is due to improper input validation of an email with an attachment and modified Multipurpose Internet Mail Extensions (MIME) header. An attacker could exploit this vulnerability by sending a malformed email message with an attachment. A successful exploit could allow the attacker to bypass configured message filters to drop the email. The email may not be RFC compliant. However, some mail clients could still allow users to read the email, which may not have been properly filtered by the device.

There are no workarounds that address this vulnerability.

This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170607-esa1 [“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170607-esa1”]