Krzysztof Katowicz-Kowalewski discovered a vulnerability in Fail2ban, a log monitoring and system which can act on attack by preventing hosts to connect to specified services using the local firewall. When using Fail2ban to monitor Apache logs, improper input validation in log parsing could enable a remote attacker to trigger an IP ban on arbitrary addresses, thus causing a denial of service.

For the oldstable distribution (squeeze), this problem has been fixed in version 0.8.4-3+squeeze2. For the stable distribution (wheezy), this problem has been fixed in version 0.8.6-3wheezy2. For the testing distribution (jessie), this problem has been fixed in version 0.8.10-1. For the unstable distribution (sid), this problem has been fixed in version 0.8.10-1. We recommend that you upgrade your fail2ban packages.

Monitors log files (e.g. /var/log/auth.log, /var/log/apache/access.log) and temporarily or persistently bans failure-prone addresses by updating existing firewall rules. The software was completely rewritten at version 0.7.0 and now allows easy specification of different actions to be taken such as to ban an IP using iptables or hostsdeny rules, or simply to send a notification email. Currently, by default, supports ssh/apache/vsftpd but configuration can be easily extended for monitoring any other ASCII file. All filters and actions are given in the config files, thus fail2ban can be adopted to be used with a variety of files and firewalls.

fail2ban on Debian Linux

This check tests the installed software version using the apt package manager.

• http://www.debian.org/security/2013/dsa-2708.html

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Updated on 2015-03-25