{"id":"CVE-2026-109786","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-109786","generatedAt":"2026-10-28T03:32:24.814Z","title":"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…","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.","published":"2026-10-13T03:16:41.000Z","lastModified":"2026-10-16T19:56:00.000Z","status":"Awaiting Analysis","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"cwe":["CWE-117"],"affected":[],"epss":{"score":0.00314,"percentile":0.24209,"date":"2026-10-27","history":[{"date":"2026-10-13","score":0.00314,"percentile":0.2254}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.31%). Track it; it rarely justifies an emergency change on its own."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-13T03:16:41.000Z","detail":{"score":"5.3","severity":"MEDIUM","publishedAt":"2026-10-13T03:16:40.943Z"},"summary":"New CVE, medium severity (CVSS 5.3)."}],"references":[{"url":"https://coredump.ws/repos/mail-hardening.git/","source":"cve@mitre.org"},{"url":"https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187","source":"cve@mitre.org"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-109786","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}