CVE-2026-39971

{
  "id": "CVE-2026-39971",
  "sourceIdentifier": "[email protected]",
  "published": "2026-04-15T04:17:39.763",
  "lastModified": "2026-10-26T22:10:00.163",
  "vulnStatus": "Analyzed",
  "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['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."
    },
    {
      "lang": "es",
      "value": "Serendipity es un motor de weblog impulsado por PHP. En las versiones 2.6-beta2 e inferiores, la funcionalidad de envío de correo electrónico en include/functions.inc.php inserta $_SERVER[’HTTP_HOST’] directamente en el encabezado SMTP Message-ID sin validación, y la función de saneamiento existente serendipity_isResponseClean() no se llama en HTTP_HOST antes de incrustarlo. Un atacante que puede controlar el encabezado Host durante una acción que desencadena un correo electrónico, como notificaciones de comentarios o correos electrónicos de suscripción, puede inyectar encabezados SMTP arbitrarios en los correos electrónicos salientes. Esto permite la suplantación de identidad, el secuestro de respuestas a través de la manipulación del encadenamiento de Message-ID, y el abuso de la reputación del correo electrónico a través del dominio del atacante incrustado en los encabezados de correo legítimos. Este problema ha sido solucionado en la versión 2.6.0."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "s9y",
          "product": "Serendipity",
          "versions": [
            {
              "version": "< 2.6.0",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
          "baseScore": 7.2,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "CHANGED",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.7
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-04-15T16:20:55.327550Z",
          "id": "CVE-2026-39971",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-113"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:s9y:serendipity:*:*:*:*:*:*:*:*",
              "versionEndExcluding": "2.6.0",
              "matchCriteriaId": "25355E06-ECC8-4A6C-ADB1-1A8ED17E5ABF"
            },
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:s9y:serendipity:2.6.0:beta1:*:*:*:*:*:*",
              "matchCriteriaId": "D31C5F34-5B83-4955-870B-0D1AC375DA24"
            }
          ]
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/s9y/Serendipity/releases/tag/2.6.0",
      "source": "[email protected]",
      "tags": [
        "Patch"
      ]
    },
    {
      "url": "https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r",
      "source": "[email protected]",
      "tags": [
        "Exploit",
        "Mitigation",
        "Vendor Advisory"
      ]
    }
  ]
}