{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-109786",
        "assignerOrgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
        "state": "PUBLISHED",
        "assignerShortName": "mitre",
        "dateReserved": "2026-10-13T02:40:12.792Z",
        "datePublished": "2026-10-13T02:40:13.899Z",
        "dateUpdated": "2026-10-13T02:40:13.899Z"
    },
    "containers": {
        "cna": {
            "affected": [
                {
                    "defaultStatus": "unknown",
                    "modules": [
                        "sshd filter"
                    ],
                    "platforms": [
                        "Linux",
                        "Unix"
                    ],
                    "product": "fail2ban",
                    "programFiles": [
                        "config/filter.d/sshd.conf"
                    ],
                    "repo": "https://github.com/fail2ban/fail2ban",
                    "vendor": "fail2ban",
                    "versions": [
                        {
                            "lessThanOrEqual": "1.1.1",
                            "status": "affected",
                            "version": "0.10.5",
                            "versionType": "custom"
                        }
                    ]
                }
            ],
            "configurations": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "The sshd jail is enabled with the stock filter.d/sshd.conf (any mode: normal, the default, extra, or aggressive). Before 1.1.1 the filter only matches log lines from a process named sshd (OpenSSH before 10, or systems that log as sshd); 1.1.1 also matches OpenSSH 10's sshd-session."
                        }
                    ],
                    "value": "The sshd jail is enabled with the stock filter.d/sshd.conf (any mode: normal, the default, extra, or aggressive). Before 1.1.1 the filter only matches log lines from a process named sshd (OpenSSH before 10, or systems that log as sshd); 1.1.1 also matches OpenSSH 10's sshd-session."
                }
            ],
            "descriptions": [
                {
                    "lang": "en",
                    "value": "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": [
                {
                    "cvssV3_1": {
                        "attackComplexity": "LOW",
                        "attackVector": "NETWORK",
                        "availabilityImpact": "LOW",
                        "baseScore": 5.3,
                        "baseSeverity": "MEDIUM",
                        "confidentialityImpact": "NONE",
                        "integrityImpact": "NONE",
                        "privilegesRequired": "NONE",
                        "scope": "UNCHANGED",
                        "userInteraction": "NONE",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
                        "version": "3.1"
                    },
                    "format": "CVSS",
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "GENERAL"
                        }
                    ]
                }
            ],
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-117",
                            "description": "CWE-117 Improper Output Neutralization for Logs",
                            "lang": "en",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
                "shortName": "mitre",
                "dateUpdated": "2026-10-13T02:40:13.899Z"
            },
            "references": [
                {
                    "tags": [
                        "patch"
                    ],
                    "url": "https://github.com/fail2ban/fail2ban/commit/ddd879d22664904ace24e1255ac6571808c58187"
                },
                {
                    "tags": [
                        "related"
                    ],
                    "url": "https://coredump.ws/repos/mail-hardening.git/"
                }
            ],
            "solutions": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "Apply upstream commit ddd879d22664904ace24e1255ac6571808c58187, or upgrade to the first fail2ban release after 1.1.1 that contains it."
                        }
                    ],
                    "value": "Apply upstream commit ddd879d22664904ace24e1255ac6571808c58187, or upgrade to the first fail2ban release after 1.1.1 that contains it."
                }
            ],
            "workarounds": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "Override __on_port_opt and __suff in a local filter.d/sshd.local so that only an optional \"port N\" may follow the host address, as in the upstream fix: __on_port_opt = (?: port \\d+)? and __suff = %(__on_port_opt)s(?: \\[preauth\\])?\\s*. Add the administrator's own addresses to ignoreip."
                        }
                    ],
                    "value": "Override __on_port_opt and __suff in a local filter.d/sshd.local so that only an optional \"port N\" may follow the host address, as in the upstream fix: __on_port_opt = (?: port \\d+)? and __suff = %(__on_port_opt)s(?: \\[preauth\\])?\\s*. Add the administrator's own addresses to ignoreip."
                }
            ],
            "x_generator": {
                "engine": "CVE-Request-form 0.0.1"
            },
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "operator": "OR",
                            "negate": false,
                            "cpeMatch": [
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:a:fail2ban:fail2ban:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "0.10.5",
                                    "versionEndIncluding": "1.1.1"
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    }
}