{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-39971",
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "state": "PUBLISHED",
        "assignerShortName": "GitHub_M",
        "dateReserved": "2026-04-08T00:01:47.627Z",
        "datePublished": "2026-04-14T23:35:49.305Z",
        "dateUpdated": "2026-04-15T16:22:04.004Z"
    },
    "containers": {
        "cna": {
            "title": "Serendipity: Host Header Injection leads to SMTP header injection via unvalidated HTTP_HOST",
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-113",
                            "lang": "en",
                            "description": "CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "attackComplexity": "LOW",
                        "attackVector": "NETWORK",
                        "availabilityImpact": "NONE",
                        "baseScore": 7.2,
                        "baseSeverity": "HIGH",
                        "confidentialityImpact": "LOW",
                        "integrityImpact": "LOW",
                        "privilegesRequired": "NONE",
                        "scope": "CHANGED",
                        "userInteraction": "NONE",
                        "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
                        "version": "3.1"
                    }
                }
            ],
            "references": [
                {
                    "name": "https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r",
                    "tags": [
                        "x_refsource_CONFIRM"
                    ],
                    "url": "https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r"
                },
                {
                    "name": "https://github.com/s9y/Serendipity/releases/tag/2.6.0",
                    "tags": [
                        "x_refsource_MISC"
                    ],
                    "url": "https://github.com/s9y/Serendipity/releases/tag/2.6.0"
                }
            ],
            "affected": [
                {
                    "vendor": "s9y",
                    "product": "Serendipity",
                    "versions": [
                        {
                            "version": "< 2.6.0",
                            "status": "affected"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
                "shortName": "GitHub_M",
                "dateUpdated": "2026-04-14T23:35:49.305Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the email sending functionality in include/functions.inc.php inserts $_SERVER['HTTP_HOST'] directly into the Message-ID SMTP header without validation, and the existing sanitization function serendipity_isResponseClean() is not called on HTTP_HOST before embedding it. An attacker who can control the Host header during an email-triggering action such as comment notifications or subscription emails can inject arbitrary SMTP headers into outgoing emails. This enables identity spoofing, reply hijacking via manipulated Message-ID threading, and email reputation abuse through the attacker's domain being embedded in legitimate mail headers. This issue has been fixed in version 2.6.0."
                }
            ],
            "source": {
                "advisory": "GHSA-458g-q4fh-mj6r",
                "discovery": "UNKNOWN"
            }
        },
        "adp": [
            {
                "metrics": [
                    {
                        "other": {
                            "type": "ssvc",
                            "content": {
                                "timestamp": "2026-04-15T16:20:55.327550Z",
                                "id": "CVE-2026-39971",
                                "options": [
                                    {
                                        "Exploitation": "poc"
                                    },
                                    {
                                        "Automatable": "yes"
                                    },
                                    {
                                        "Technical Impact": "partial"
                                    }
                                ],
                                "role": "CISA Coordinator",
                                "version": "2.0.3"
                            }
                        }
                    }
                ],
                "title": "CISA ADP Vulnrichment",
                "providerMetadata": {
                    "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
                    "shortName": "CISA-ADP",
                    "dateUpdated": "2026-04-15T16:22:04.004Z"
                }
            }
        ]
    }
}