CVE-2007-4321: FAIL2BAN

Medium severity, CVSS 6.8. EPSS: 5.7% chance of exploitation in the next 30 days.

fail2ban 0.8 and earlier does not properly parse sshd log files, which allows remote attackers to add arbitrary hosts to the /etc/hosts.deny file and cause a denial of service by adding arbitrary IP addresses to the sshd log file, as demonstrated by logging in via ssh with a client protocol version identification containing an IP address string, a different vector than CVE-2006-6302.

Affected products

• FAIL2BAN FAIL2BAN: version 0.8 only

Published 2007-08-14. Last modified 2026-06-16.