Fail2ban is a tool for parsing log files and banning IP addresses which make too many password failures.
A vulnerability has been discovered in Fail2ban when parsing log files.
A remote attacker could send specially crafted SSH login banners to the vulnerable host, which would prevent any ssh connection to the host and result in a Denial of Service.
There is no known workaround at this time.
All Fail2ban users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=net-analyzer/fail2ban-0.8.0-r1"