CVE-2026-75759

Estado: AplazadaAlta (7.6)—

Improper Verification of Cryptographic Signature vulnerability in erlef oidcc allows an unauthenticated attacker to impersonate an arbitrary user via an encrypted ID token or JARM response carrying no nested signature. OpenID Connect Core 1.0 section 2 requires that an encrypted ID token be signed then encrypted, with the result being a Nested JWT, and JARM processing rule 5 requires the client to check the signature unconditionally. oidcc instead accepted a JWE wrapping unsigned claims as fully validated, so anyone holding the relying party's public encryption key could mint a token with an arbitrary sub, iss, and aud without possessing the provider's signing key.

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In oidcc_jwt_util:verify_decrypted_token/4, a decrypted payload that is not a signed JWS fell back to parsing the plaintext claims and returning them with no verifying key. oidcc_token:int_validate_jwt/4 then matched on the JOSE structure type rather than on whether a signature had been verified, and returned success. The JARM path in oidcc_token:validate_jarm/3 is reachable through the browser front channel. UserInfo responses are not affected, because OpenID Connect Core 1.0 section 5.3.2 permits them to be encrypted without also being signed.

This issue affects oidcc: from 3.2.0-beta.1 before 3.9.0.

CVSS

Versión: 4.0
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/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
Puntuación base: 7.6

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.22%
Percentil entre todas las CVEs puntuadas: 11
Fecha de la puntuación: 5/10/2026

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.

ExplotaciónT1203 Exploitation for Client Executionexecution85 %
Impacto principalT1078.004 Cloud Accountsstealth · persistence · privilege escalation · initial access80 %
Impacto secundarioT1556.006 Multi-Factor Authenticationdefense impairment · persistence · credential access75 %

UI:P + interacción del usuario (aceptación de token) = T1203. Impacto: suplantación de usuario (T1078.004) por forja de JWT sin verificación de firma; modificación de configuración de autenticación (T1556.006) al aceptar tokens no firmados.

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

User Account Management Multi-factor Authentication Active Directory Configuration User Training Privileged Account Management Password Policies

Tecnologías afectadas (1)

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

Erlef — Oidcc^AI

CWE

CWE-347

Referencias

JSON original (NVD)

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  "id": "CVE-2026-75759",
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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          "role": "CISA Coordinator",
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          "attackVector": "NETWORK",
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          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/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",
          "exploitMaturity": "NOT_DEFINED",
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          "modifiedAttackVector": "NOT_DEFINED",
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          "modifiedAttackComplexity": "NOT_DEFINED",
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          "vulnConfidentialityImpact": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
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          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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      "affectedData": [
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          "vendor": "erlef",
          "modules": [
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          "collectionURL": "https://repo.hex.pm",
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              "name": "oidcc_jwt_util:verify_decrypted_token/4"
            },
            {
              "name": "oidcc_jwt_util:verify_not_none_alg/1"
            },
            {
              "name": "oidcc_token:int_validate_jwt/4"
            },
            {
              "name": "oidcc_token:validate_id_token/3"
            },
            {
              "name": "oidcc_token:validate_jarm/3"
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      ]
    }
  ],
  "published": "2026-08-30T02:18:30.110",
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-75759.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/erlef/oidcc/commit/5f62fbccdae8526ff62653b8901657a6c1400fd9",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "description": [
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          "lang": "en",
          "value": "CWE-347"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Improper Verification of Cryptographic Signature vulnerability in erlef oidcc allows an unauthenticated attacker to impersonate an arbitrary user via an encrypted ID token or JARM response carrying no nested signature. OpenID Connect Core 1.0 section 2 requires that an encrypted ID token be signed then encrypted, with the result being a Nested JWT, and JARM processing rule 5 requires the client to check the signature unconditionally. oidcc instead accepted a JWE wrapping unsigned claims as fully validated, so anyone holding the relying party's public encryption key could mint a token with an arbitrary sub, iss, and aud without possessing the provider's signing key.\n\nIn oidcc_jwt_util:verify_decrypted_token/4, a decrypted payload that is not a signed JWS fell back to parsing the plaintext claims and returning them with no verifying key. oidcc_token:int_validate_jwt/4 then matched on the JOSE structure type rather than on whether a signature had been verified, and returned success. The JARM path in oidcc_token:validate_jarm/3 is reachable through the browser front channel. UserInfo responses are not affected, because OpenID Connect Core 1.0 section 5.3.2 permits them to be encrypted without also being signed.\n\nThis issue affects oidcc: from 3.2.0-beta.1 before 3.9.0."
    }
  ],
  "lastModified": "2026-09-01T21:15:00.147",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}