Courier MTA: Denial of Service vulnerability

Background

Courier MTA is an integrated mail and groupware server based on open protocols.

Description

Courier MTA has fixed a security issue relating to usernames containing the “=” character, causing high CPU utilization.

Impact

An attacker could exploit this vulnerability by sending a specially crafted email to a mail gateway running a vulnerable version of Courier MTA.

Workaround

There is no known workaround at this time.

Resolution

All Courier MTA users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=mail-mta/courier-0.53.2"