CVE-2026-109786: fail2ban 0.10.5 through 1.1.1

Affected technology

fail2ban · 0.10.5 through 1.1.1
fail2ban

Description’s affected range: through 1.1.1 before ddd879d

Component: sshd filter
File: config/filter.d/sshd.conf

Attack conditions (Vendor/CNA, CVSS 3.1): Network (remote) · No privileges required · No user interaction required

What an attacker can do

A remote unauthenticated attacker can use a username such as "x VICTIM-SOURCE-IP-ADDRESS on" to make fail2ban associate failed login attempts with an arbitrary source IP address and ban it (e.g., to block logins from a legitimate user). Vendor/CNA’s CVSS 3.1 assessment (base score 5.3/10) rates confidentiality and integrity impact as none; availability impact as low.