{"id":"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":"2026-10-14T02:47:59.074403203Z","published":"2026-10-13T02:40:13.899Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109786.json","cna_assigner":"mitre","cwe_ids":["CWE-117"]},"references":[{"type":"WEB","url":"https://coredump.ws/repos/mail-hardening.git/"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109786.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109786"},{"type":"FIX","url":"https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187"},{"type":"PACKAGE","url":"https://github.com/fail2ban/fail2ban"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/fail2ban/fail2ban","events":[{"introduced":"b25d8565fc23da58f97d1da649b46d27fb80b64a"},{"fixed":"f60978618a101427b06924fc932b44350fec2b63"},{"fixed":"ddd879d22664904ace24e1255ac6571808c58187"}],"database_specific":{"extracted_events":[{"introduced":"0.10.5"},{"fixed":"1.1.1"}],"source":["DESCRIPTION","REFERENCES"]}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/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"}]}