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CVE-2021-40528

Estado: ModificadaMedia (5.9)—

The ElGamal implementation in Libgcrypt before 1.9.4 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP.

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)

Gnupg — Libgcrypt

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-40528",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-40528",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2025-06-09T15:12:20.359985Z"
        }
      }
    ],
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 2.6,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:H/Au:N/C:P/I:N/A:N",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "LOW",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 4.9,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
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        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
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          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
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          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.2
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
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  ],
  "published": "2021-09-06T19:15:07.587",
  "references": [
    {
      "url": "https://eprint.iacr.org/2021/923",
      "tags": [
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        "Third Party Advisory"
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      "source": "cve@mitre.org"
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    {
      "url": "https://git.gnupg.org/cgi-bin/gitweb.cgi?p=libgcrypt.git%3Ba=commit%3Bh=3462280f2e23e16adf3ed5176e0f2413d8861320",
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    },
    {
      "url": "https://ibm.github.io/system-security-research-updates/2021/07/20/insecurity-elgamal-pt1",
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    },
    {
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      "source": "cve@mitre.org"
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
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      "tags": [
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      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-327"
        }
      ]
    },
    {
      "type": "Secondary",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "description": [
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          "lang": "en",
          "value": "CWE-327"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "The ElGamal implementation in Libgcrypt before 1.9.4 allows plaintext recovery because, during interaction between two cryptographic libraries, a certain dangerous combination of the prime defined by the receiver's public key, the generator defined by the receiver's public key, and the sender's ephemeral exponents can lead to a cross-configuration attack against OpenPGP."
    },
    {
      "lang": "es",
      "value": "Una implementación de ElGamal en Libgcrypt versiones anteriores a 1.9.4, permite una recuperación de texto plano porque, durante la interacción entre dos bibliotecas criptográficas, una determinada combinación peligrosa del primo definido por la clave pública del receptor, el generador definido por la clave pública del receptor y los exponentes efímeros del emisor puede conllevar a un ataque de configuración cruzada contra OpenPGP."
    }
  ],
  "lastModified": "2026-06-17T04:07:05.660",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "criteria": "cpe:2.3:a:gnupg:libgcrypt:*:*:*:*:*:*:*:*",
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              "versionEndExcluding": "1.9.4"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}