Cisco Email Security Appliance Malformed DGN File Attachment Denial of Service Vulnerability

A vulnerability in the email message filtering feature of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

The vulnerability exists because the message filtering feature of the affected software does not properly validate compressed message attachments that contain malformed Design (DGN) files. An attacker could exploit this vulnerability by sending a crafted email message, which has a compressed attachment containing a malformed DGN file, through an affected device. While the affected software filters the attachment, memory could be consumed at a high rate and ultimately exhausted, causing the filtering process to restart and resulting in a DoS condition. After the filtering process restarts, the software resumes filtering for the same attachment, causing the filtering process to exhaust memory and restart again. A successful exploit of this vulnerability could allow the attacker to cause a repeated DoS condition.

Cisco has released software updates that address this vulnerability. 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-20161026-esa1[“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20161026-esa1”]