CVE-2026-109786CWE-117

CVE-2026-109786

Medium · published October 13, 2026

CVSS v3.1
5.3
EPSS
0%
Percentile
23.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS v4.0
Not supplied
EPSS
0.00314 · 23.1th percentile
Weakness
CWE-117 · Improper Output Neutralization for Logs
Published
2026-10-13T07:16Z
References (2)
https://coredump.ws/repos/mail-hardening.git/ · [email protected]https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187 · [email protected]
EPSS history
Timeline
  • 14 OCT 03:27Z
    EPSS moved — → 0%
    epss
  • 13 OCT 02:40Z
    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
    cvelistv5
  • 13 OCT 02:40Z
    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
    cvelistv5