Fail2ban is a tool for parsing log files and banning IP addresses which show suspicious behavior.
Multiple vulnerabilities have been discovered in Fail2ban. Please review the CVE identifiers referenced below for details.
A remote attacker could send a crafted URL to a web site which, when parsed by Fail2ban, would deny a specific IP address. Also, errors in regular expressions within certain filters can cause arbitrary IP addresses to be banned. Furthermore, a local attacker could perform symlink attacks to overwrite arbitrary files with the privileges of the user running the application.
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-0.8.12