CVE catalog

CVE-2026-109786

In fail2ban 0.10.5 through 1.1.1 before ddd879d, the…

[CVE catalog]

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.

Severity
Medium · CVSS 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published
Updated
Source
[NVD] · [CVE record]
EPSS
0.31% · Oct 27, 2026

Projects and upstream resources

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Version impact has not been established. The original provider fields are retained below.

Provider details and historical evidence
Original provider fields
{
  "package_releases": [
    {
      "name": "fail2ban",
      "status": "vulnerable",
      "release": "sid",
      "version": "1.1.1-1"
    },
    {
      "name": "fail2ban",
      "status": "vulnerable",
      "release": "forky",
      "version": "1.1.1-1"
    },
    {
      "name": "fail2ban",
      "status": "vulnerable",
      "release": "trixie",
      "version": "1.1.0-8"
    },
    {
      "name": "fail2ban",
      "status": "vulnerable",
      "release": "bookworm",
      "version": "1.0.2-2"
    }
  ],
  "fixed_versions": [
    {
      "bug": 1151199,
      "name": "fail2ban",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "not yet assigned",
      "fixed_version": ""
    },
    {
      "bug": 1151199,
      "name": "fail2ban",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "not yet assigned",
      "fixed_version": ""
    },
    {
      "bug": 1151199,
      "name": "fail2ban",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "not yet assigned",
      "fixed_version": ""
    },
    {
      "bug": 1151199,
      "name": "fail2ban",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "not yet assigned",
      "fixed_version": ""
    }
  ],
  "distribution_packages": []
}

[Debian bug #1151199]

Publisher notes

[trixie] fail2ban: Minor issue [bookworm] fail2ban: Minor issue

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

  • [fail2ban]Unknown
    Details (2)

    • 1.0.2-2 · all · bookworm

      Affected

      nvd · fail2ban · debian · bookworm; nvd · fail2ban · debian · 12

    • 1.0.2-2 · all · bookworm

      Affected

      nvd · fail2ban · debian · bookworm; nvd · fail2ban · debian · 12

[Debian 13 (Trixie)]

  • [fail2ban]Unknown
    Details (2)

    • 1.1.0-8 · all · trixie

      Affected

      nvd · fail2ban · debian · 13

    • 1.1.0-8 · all · trixie

      Affected

      nvd · fail2ban · debian · 13

Observed:

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]