CVE-2026-109786 Details
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.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Oct 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://coredump.ws/repos/mail-hardening.git/ | [email protected] | |
| https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187 | [email protected] |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-117 | Improper Output Neutralization for Logs | [email protected] |
Affected Products
No affected product data is available for this CVE.
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Oct 15, 2026 | CVE Modified | CISA-ADP |
| Oct 13, 2026 | New CVE Received | [email protected] |