{"id":"CVE-2026-109786","published":"2026-10-13T03:16:40.943","lastModified":"2026-10-16T19:55:59.740","description":"In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf) accepts an \"on <token>\" suffix after the host address. Because OpenSSH logs the offered username verbatim, 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). The default filter mode is affected.","cvssScore":5.3,"cvssSeverity":"MEDIUM","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwes":["CWE-117"],"vendors":[],"products":[],"references":[{"url":"https://coredump.ws/repos/mail-hardening.git/","tags":[]},{"url":"https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187","tags":[]}],"exploitRefs":[{"url":"https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187","tags":[]}],"hasPoc":true,"ai":null}