CVE-2026-109786

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Source
https://cve.org/CVERecord?id=CVE-2026-109786
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-109786.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-109786
Downstream
Published
2026-10-13T02:40:13Z
Modified
2026-10-14T02:47:59Z
Severity
  • 5.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L CVSS Calculator
Summary
[none]
Details

In fail2ban 0.10.5 through 1.1.1 before ddd879d, the sshd filter (config/filter.d/sshd.conf) accepts an "on " 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.

Database specific 
{
    "cna_assigner":  "mitre",
    "cwe_ids":  [
        "CWE-117"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109786.json"
}
References

Affected packages

Git / github.com/fail2ban/fail2ban

Affected ranges

Type
GIT
Repo
https://github.com/fail2ban/fail2ban
Events
Introduced
b25d8565fc23da58f97d1da649b46d27fb80b64a
Fixed
f60978618a101427b06924fc932b44350fec2b63
Fixed
ddd879d22664904ace24e1255ac6571808c58187
Database specific
Show details 
{
    "extracted_events":  [
        {
            "introduced":  "0.10.5"
        },
        {
            "fixed":  "1.1.1"
        }
    ],
    "source":  [
        "DESCRIPTION",
        "REFERENCES"
    ]
}

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-109786.json"