FKIE_CVE-2026-39971

Vulnerability from fkie_nvd - Published: 2026-04-15 04:17 - Updated: 2026-04-23 13:59
Severity ?
7.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Summary
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.
References
security-advisories@github.comhttps://github.com/s9y/Serendipity/releases/tag/2.6.0Patch
security-advisories@github.comhttps://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6rExploit, Vendor Advisory, Mitigation
Impacted products
Vendor Product Version
s9y serendipity *
s9y serendipity 2.6.0
To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:s9y:serendipity:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "25355E06-ECC8-4A6C-ADB1-1A8ED17E5ABF",
              "versionEndExcluding": "2.6.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:s9y:serendipity:2.6.0:beta1:*:*:*:*:*:*",
              "matchCriteriaId": "D31C5F34-5B83-4955-870B-0D1AC375DA24",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "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[\u0027HTTP_HOST\u0027] 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\u0027s domain being embedded in legitimate mail headers. This issue has been fixed in version 2.6.0."
    }
  ],
  "id": "CVE-2026-39971",
  "lastModified": "2026-04-23T13:59:19.810",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "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"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-04-15T04:17:39.763",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/s9y/Serendipity/releases/tag/2.6.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory",
        "Mitigation"
      ],
      "url": "https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-113"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}


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