CVE-2026-109786
- State
- Published
- Severity
- 5.3 Medium
- Published
- Oct 13, 2026
- Updated
- Oct 15, 2026
- Reserved
- Oct 13, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | mitre |
Weaknesses
- CWE-117 Improper Output Neutralization for Logs
Affected Products
| Product | Versions |
|---|---|
fail2banfail2ban |
|
References
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