Fail2ban: Denial of service

Background

Fail2ban monitors log files for failed authentication attempts and can block hosts responsible for repeated attacks.

Description

A flaw in the method used to parse log entries allows remote, unauthenticated attackers to forge authentication attempts from other hosts.

Impact

A remote attacker can add arbitrary hosts to the block list, denying legitimate users access to a resource.

Workaround

There is no known workaround at this time.

Resolution

All Fail2ban users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=net-analyzer/fail2ban-0.6.2"