{"id":"CVE-2026-109786","aliases":["DEBIAN-CVE-2026-109786","EUVD-2026-98268","GHSA-xw36-3g63-5wfw","UBUNTU-CVE-2026-109786"],"status":"published","title":"In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf)...","description":"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.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00314,"percentile":0.24681,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-117"],"published":"2026-10-13T02:40:13Z","modified":"2026-11-11T02:47:37Z","affected":[{"source":"osv","ecosystem":"Debian:12","package":"fail2ban","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"]},{"source":"osv","ecosystem":"Debian:13","package":"fail2ban","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"]},{"source":"osv","ecosystem":"Debian:14","package":"fail2ban","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"]},{"source":"osv","ecosystem":"Ubuntu:Pro:14.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.10-3","0.8.11~pre1+git29-gccd2657-1","0.8.11-1","0.8.11-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.9.3-1","0.9.3-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.9.7-2","0.10.2-1","0.10.2-2","0.10.2-2ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.10.2-2.1","0.11.1-1","0.11.1-1ubuntu0.1~esm1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.11.2-2","0.11.2-4","0.11.2-5","0.11.2-6"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.2-2","1.0.2-3","1.0.2-3ubuntu0.1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.0-9","1.1.0-10","1.1.0-11"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"fail2ban","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.0-8","1.1.0-9"]}],"products":[{"vendor":"fail2ban","product":"fail2ban"}],"references":[{"url":"https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187","tags":["patch","fix","report"]},{"url":"https://coredump.ws/repos/mail-hardening.git/","tags":["related","web","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109786","tags":["advisory"]},{"url":"https://coredump.ws/repos/mail-hardening.git"},{"url":"https://github.com/advisories/GHSA-xw36-3g63-5wfw"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109786.json","tags":["advisory"]},{"url":"https://github.com/fail2ban/fail2ban","tags":["package"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-109786","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-109786","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-109786","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-109786","description":"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.","status":"published","published":"2026-10-13T02:40:13.899Z","modified":"2026-10-15T15:04:19.106Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-117"],"updated_at":"2026-11-02T14:20:11.581788Z"}],"euvd":[{"id":"EUVD-2026-98268","description":"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.","status":"published","published":"2026-10-13T02:40:13Z","modified":"2026-10-15T15:04:19Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T17:00:14.20041Z"}],"ghsa":[{"id":"GHSA-xw36-3g63-5wfw","title":"In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf)...","description":"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.","status":"published","published":"2026-10-13T03:30:36Z","modified":"2026-10-13T03:30:37Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-117"],"updated_at":"2026-11-02T15:13:10.125536Z"}],"nvd":[{"id":"CVE-2026-109786","description":"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.","status":"published","published":"2026-10-13T03:16:40.943Z","modified":"2026-10-16T19:55:59.74Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"secondary"}],"cwes":["CWE-117"],"updated_at":"2026-11-02T14:12:56.72789Z"}],"osv":[{"id":"CVE-2026-109786","description":"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.","status":"published","published":"2026-10-13T02:40:13.899Z","modified":"2026-11-11T10:47:23.623367336Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-117"],"updated_at":"2026-11-11T03:22:28.447808Z"},{"id":"DEBIAN-CVE-2026-109786","description":"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.","status":"published","published":"2026-10-13T03:16:40.943Z","modified":"2026-10-23T17:47:35.049161922Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:45:49.381767Z"},{"id":"UBUNTU-CVE-2026-109786","description":"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.","status":"published","published":"2026-10-13T03:16:00Z","modified":"2026-10-28T17:50:33Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T16:55:59.130573Z"}]}}