It was reported  that fail2ban improperly parses Apache log files, due to improper regular expressions. This could allow a remote attacker to send a crafted URL to a web site which, when parsed by fail2ban, would deny a specific IP address (not the remote attacker's IP).
This was reported against fail2ban 0.8.9, but earlier versions use the same regular expression. This has not yet been addressed upstream; the original report suggests replacement regular expressions, but in my (limited) testing they do not seem to work (testing using fail2ban-regex).
Created fail2ban tracking bugs for this issue
Affects: fedora-all [bug 973757]
Affects: epel-all [bug 973758]
The CVE identifier of CVE-2013-2178 has been assigned to this issue:
fail2ban-0.8.10-1.fc18 has been pushed to the Fedora 18 stable repository. If problems still persist, please make note of it in this bug report.
fail2ban-0.8.10-1.el6 has been pushed to the Fedora EPEL 6 stable repository. If problems still persist, please make note of it in this bug report.
This CVE Bugzilla entry is for community support informational purposes only as it does not affect a package in a commercially supported Red Hat product. Refer to the dependent bugs for status of those individual community products.