Cisco AsyncOS TCP Flood Denial of Service Vulnerability

A vulnerability in the network stack of Cisco AsyncOS for Cisco Email Security Appliance (ESA), Cisco Content Security Management Appliance (SMA) and Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to exhaust all available memory, preventing the affected device from accepting new TCP connections.

The vulnerability is due to improper handling of TCP packets sent at a high rate. An attacker could exploit this vulnerability by sending crafted TCP packets to the affected system.

Note: A full device reload is needed to recover the system to an operational state.

Cisco has released software updates that address this vulnerability. There are no workarounds that mitigate this vulnerability. This advisory is available at the following link:

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151104-aos[“https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20151104-aos”]