CVE-2026-41319

{
  "id": "CVE-2026-41319",
  "sourceIdentifier": "[email protected]",
  "published": "2026-04-24T04:16:20.400",
  "lastModified": "2026-10-26T22:10:00.163",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "MailKit is a cross-platform mail client library built on top of MimeKit. A STARTTLS Response Injection vulnerability in versions prior to 4.16.0 allows a Man-in-the-Middle attacker to inject arbitrary protocol responses across the plaintext-to-TLS trust boundary, enabling SASL authentication mechanism downgrade (e.g., forcing PLAIN instead of SCRAM-SHA-256). The internal read buffer in `SmtpStream`, `ImapStream`, and `Pop3Stream` is not flushed when the underlying stream is replaced with `SslStream` during STARTTLS upgrade, causing pre-TLS attacker-injected data to be processed as trusted post-TLS responses. Version 4.16.0 patches the issue."
    },
    {
      "lang": "es",
      "value": "MailKit es una biblioteca de cliente de correo multiplataforma construida sobre MimeKit. Una vulnerabilidad de inyección de respuesta STARTTLS en versiones anteriores a la 4.16.0 permite a un atacante man-in-the-middle inyectar respuestas de protocolo arbitrarias a través del límite de confianza de texto plano a TLS, lo que permite la degradación del mecanismo de autenticación SASL (por ejemplo, forzar PLAIN en lugar de SCRAM-SHA-256). El búfer de lectura interno en ’SmtpStream’, ’ImapStream’ y ’Pop3Stream’ no se vacía cuando el flujo subyacente es reemplazado con ’SslStream’ durante la actualización STARTTLS, lo que hace que los datos inyectados por el atacante pre-TLS sean procesados como respuestas post-TLS confiables. La versión 4.16.0 corrige el problema."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "jstedfast",
          "product": "MailKit",
          "versions": [
            {
              "version": "< 4.16.0",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "REQUIRED",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 3.6
      },
      {
        "source": "[email protected]",
        "type": "Primary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-04-25T01:46:14.462850Z",
          "id": "CVE-2026-41319",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-74"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:jstedfast:mailkit:*:*:*:*:*:*:*:*",
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  "references": [
    {
      "url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr",
      "source": "[email protected]",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ]
    },
    {
      "url": "https://github.com/jstedfast/MailKit/security/advisories/GHSA-9j88-vvj5-vhgr",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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}