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CVE-2026-45446

Estado: AnalizadaMedia (4.8)—

Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) mishandle the authentication of AAD (Additional Authenticated Data) with an empty ciphertext allowing a forgery of such messages.

Impact summary: An attacker can forge empty messages with arbitrary AAD to the victim's application using these ciphers.

AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD modes: they accept a key, nonce, optional AAD (bytes that are authenticated but not encrypted), and plaintext, and produces ciphertext plus a 16-byte tag. On decrypt, `EVP_DecryptFinal_ex()` is documented to return success only if the tag is verified succesfully.

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In OpenSSL's provider implementation of these ciphers, the expected tag is computed only when decryption function is invoked with non-empty data. If the caller supplies AAD and then calls `EVP_DecryptFinal_ex()` without invocation of the ciphertext update, which can happen when the received ciphertext length is zero, the tag is never recalculated and still holds its all-zeros value.

When AES-GCM-SIV is used, an attacker who sends arbitrary AAD, empty ciphertext, and all-zeros tag passes authentication under any key they do not know, single-shot. When AES-SIV is used, for mounting the attack it's necessary for the application to reuse the decryption context without resetting the key.

AES-SIV is implemented since OpenSSL 3.0. AES-GCM-SIV is implemented since OpenSSL 3.2.

No protocols implemented in OpenSSL itself (TLS/CMS/PKCS7/HPKE/QUIC) support either AES-GCM-SIV or AES-SIV. To mount an attack, the applications must implement their own protocol and use the EVP interface. Also they must skip the ciphertext update when a message with an empty ciphertext arrives.

The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue, as these algorithms are not FIPS approved and the affected code is outside the OpenSSL FIPS module boundary.

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).

Tecnologías afectadas (1)

Openssl — Openssl

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-45446",
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          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2026-06-09T18:48:41.903041Z"
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          "integrityImpact": "LOW",
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      "value": "Issue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV\n(RFC 8452) mishandle the authentication of AAD (Additional Authenticated\nData) with an empty ciphertext allowing a forgery of such messages.\n\nImpact summary: An attacker can forge empty messages with arbitrary AAD\nto the victim's application using these ciphers.\n\nAES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD\nmodes: they accept a key, nonce, optional AAD (bytes that are authenticated\nbut not encrypted), and plaintext, and produces ciphertext plus a 16-byte\ntag. On decrypt, `EVP_DecryptFinal_ex()` is documented to return success only\nif the tag is verified succesfully.\n\nIn OpenSSL's provider implementation of these ciphers, the expected tag is\ncomputed only when decryption function is invoked with non-empty data.\nIf the caller supplies AAD and then calls `EVP_DecryptFinal_ex()` without\ninvocation of the ciphertext update, which can happen when the received\nciphertext length is zero, the tag is never recalculated and still holds its\nall-zeros value.\n\nWhen AES-GCM-SIV is used, an attacker who sends arbitrary AAD, empty\nciphertext, and all-zeros tag passes authentication under any key they do not\nknow, single-shot. When AES-SIV is used, for mounting the attack it's\nnecessary for the application to reuse the decryption context without\nresetting the key.\n\nAES-SIV is implemented since OpenSSL 3.0. AES-GCM-SIV is implemented since\nOpenSSL 3.2.\n\nNo protocols implemented in OpenSSL itself (TLS/CMS/PKCS7/HPKE/QUIC) support\neither AES-GCM-SIV or AES-SIV. To mount an attack, the applications must\nimplement their own protocol and use the EVP interface. Also they must skip the\nciphertext update when a message with an empty ciphertext arrives.\n\nThe FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this\nissue, as these algorithms are not FIPS approved and the affected code is\noutside the OpenSSL FIPS module boundary."
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      "value": "Resumen del problema: Las implementaciones de AES-SIV (RFC 5297) y AES-GCM-SIV (RFC 8452) manejan incorrectamente la autenticación de AAD (Datos Autenticados Adicionales) con un texto cifrado vacío, permitiendo una falsificación de dichos mensajes.\n\nResumen del impacto: Un atacante puede falsificar mensajes vacíos con AAD arbitrario a la aplicación de la víctima usando estos cifrados.\n\nAES-SIV (RFC 5297) y AES-GCM-SIV (RFC 8452) son modos AEAD resistentes al uso indebido de nonce: aceptan una clave, nonce, AAD opcional (bytes que son autenticados pero no cifrados) y texto plano, y producen texto cifrado más una etiqueta de 16 bytes. Al descifrar, 'EVP_DecryptFinal_ex()' está documentado para devolver éxito solo si la etiqueta se verifica con éxito.\n\nEn la implementación del proveedor de OpenSSL de estos cifrados, la etiqueta esperada se calcula solo cuando la función de descifrado se invoca con datos no vacíos. Si el llamador suministra AAD y luego llama a 'EVP_DecryptFinal_ex()' sin invocar la actualización del texto cifrado, lo que puede ocurrir cuando la longitud del texto cifrado recibido es cero, la etiqueta nunca se recalcula y aún mantiene su valor de todo ceros.\n\nCuando se usa AES-GCM-SIV, un atacante que envía AAD arbitrario, texto cifrado vacío y una etiqueta de todo ceros pasa la autenticación bajo cualquier clave que no conozca, de una sola vez. Cuando se usa AES-SIV, para montar el ataque es necesario que la aplicación reutilice el contexto de descifrado sin restablecer la clave.\n\nAES-SIV está implementado desde OpenSSL 3.0. AES-GCM-SIV está implementado desde OpenSSL 3.2.\n\nNingún protocolo implementado en OpenSSL mismo (TLS/CMS/PKCS7/HPKE/QUIC) soporta AES-GCM-SIV o AES-SIV. Para montar un ataque, las aplicaciones deben implementar su propio protocolo y usar la interfaz EVP. También deben omitir la actualización del texto cifrado cuando llega un mensaje con un texto cifrado vacío.\n\nLos módulos FIPS en 4.0, 3.6, 3.5, 3.4 y 3.0 no se ven afectados por este problema, ya que estos algoritmos no están aprobados por FIPS y el código afectado está fuera del límite del módulo FIPS de OpenSSL."
    }
  ],
  "lastModified": "2026-07-23T08:10:00.137",
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