Serendipity: Host Header Injection enables authentication cookie scoping to an attacker-controlled domain_CVE-2026-39963

{
    "lastseen": "",
    "description": "Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2  and below, the serendipity_setCookie() function in include/functions_config.inc.php uses $_SERVER['HTTP_HOST'] without validation as the domain parameter of setcookie(). An attacker who can influence the Host header at login time, such as via MITM, reverse proxy misconfiguration, or load balancer manipulation, can force authentication cookies including session tokens and auto-login tokens to be scoped to an attacker-controlled domain. This enables session fixation, token leakage to attacker-controlled infrastructure, and privilege escalation if an admin logs in under a poisoned Host header. This issue has been fixed in version 2.6.0.",
    "published": "2026-04-14T23:31:13.843Z",
    "modified": "2026-04-14T23:31:13.843Z",
    "type": "cve",
    "title": "Serendipity: Host Header Injection enables authentication cookie scoping to an attacker-controlled domain",
    "source": "GitHub_M",
    "references": "https://github.com/s9y/Serendipity/security/advisories/GHSA-4m6c-649p-f6gf\nhttps://github.com/s9y/Serendipity/releases/tag/2.6.0",
    "id": "CVE-2026-39963",
    "bulletinFamily": "",
    "cwe": [
        "CWE-565"
    ],
    "cvelist": null,
    "sourceData": "s9y Serendipity < 2.6.0",
    "sourceHref": "",
    "cvss": {
        "score": 6.9,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Serendipity",
    "version": "< 2.6.0",
    "vendor": "s9y",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}