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CVE-2026-44699

Estado: AplazadaCrítica (9.1)—

LibJWT is a C JSON Web Token Library. From 3.0.0 to 3.3.2, libjwt accepts an RSA JWK that does not contain an alg parameter as the verification key for an HS256/HS384/HS512 token. In the OpenSSL backend, this causes HMAC verification to run with a zero-length key, so an attacker can forge a valid JWT without knowing any secret or RSA private key. This is an algorithm-confusion authentication bypass. It affects applications that load RSA keys from JWKS where alg is omitted, which is valid JWK syntax and common in real deployments, and then choose the verification algorithm from the JWT header, for example in a kid lookup callback. This vulnerability is fixed in 3.3.3.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Vulnerabilidad de confusión de algoritmo en verificación JWT (CWE-347) que permite falsificar tokens sin secreto. Explotable remotamente (AV:N, PR:N, UI:N). Impactos: bypass de verificación de código (T1553.006) y riesgo de suplantación de identidad (T1078.001).

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Privileged Account ManagementVulnerability ScanningRestrict Registry PermissionsPassword PoliciesNetwork SegmentationMulti-factor Authentication

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Libjwt — LibjwtAI

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-44699",
  "cveTags": [],
  "metrics": {
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      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-44699",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
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            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-05-15T18:00:54.375359Z"
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    "cvssMetricV40": [
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          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
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  "published": "2026-05-15T17:16:47.783",
  "references": [
    {
      "url": "https://github.com/benmcollins/libjwt/security/advisories/GHSA-q843-6q5f-w55g",
      "source": "security-advisories@github.com"
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    }
  ],
  "lastModified": "2026-06-17T10:51:14.860",
  "sourceIdentifier": "security-advisories@github.com"
}