{"id":"DEBIAN-CVE-2026-109786","details":"In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf) accepts an \"on \u003ctoken\u003e\" 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.","modified":"2026-10-13T11:00:08.587185971Z","published":"2026-10-13T03:16:40.943Z","upstream":["CVE-2026-109786"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-109786"}],"affected":[{"package":{"name":"fail2ban","ecosystem":"Debian:12","purl":"pkg:deb/debian/fail2ban?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.2-2","1.0.2-3","1.1.0-1","1.1.0-10","1.1.0-11","1.1.0-2","1.1.0-3","1.1.0-4","1.1.0-6","1.1.0-7","1.1.0-8","1.1.0-9","1.1.1-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json"}},{"package":{"name":"fail2ban","ecosystem":"Debian:13","purl":"pkg:deb/debian/fail2ban?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.0-10","1.1.0-11","1.1.0-8","1.1.0-9","1.1.1-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json"}},{"package":{"name":"fail2ban","ecosystem":"Debian:14","purl":"pkg:deb/debian/fail2ban?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.0-10","1.1.0-11","1.1.0-8","1.1.0-9","1.1.1-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-109786.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}