ubuntu-cve-2021-40528
Vulnerability from osv_ubuntu
Published
2021-09-06 19:15
Modified
2026-04-22 07:40
Summary
Details

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.

Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.6.5-2ubuntu0.6+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.6.5-2ubuntu0.6+esm1?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.6.5-2ubuntu0.6+esm1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.3-2ubuntu1",
        "1.6.4-3",
        "1.6.4-4",
        "1.6.4-5",
        "1.6.5-2",
        "1.6.5-2ubuntu0.2",
        "1.6.5-2ubuntu0.3",
        "1.6.5-2ubuntu0.4",
        "1.6.5-2ubuntu0.5",
        "1.6.5-2ubuntu0.6"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.1-4ubuntu1.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.1-4ubuntu1.3?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.1-4ubuntu1.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.7.8-2ubuntu1",
        "1.7.9-1",
        "1.8.1-4",
        "1.8.1-4ubuntu1",
        "1.8.1-4ubuntu1.1",
        "1.8.1-4ubuntu1.2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.1-4ubuntu1.fips.3"
          },
          {
            "binary_name": "libgcrypt20-hmac",
            "binary_version": "1.8.1-4ubuntu1.fips.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:FIPS-updates:18.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.1-4ubuntu1.fips.3?arch=source\u0026distro=fips-updates/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.1-4ubuntu1.fips.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.8.1-4ubuntu1.fips.2.4",
        "1.8.1-4ubuntu1.fips.2.5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.1-4ubuntu1.fips.2.5"
          },
          {
            "binary_name": "libgcrypt20-hmac",
            "binary_version": "1.8.1-4ubuntu1.fips.2.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:FIPS:18.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.1-4ubuntu1.fips.2.5?arch=source\u0026distro=fips/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.8.1-4ubuntu1.fips.2.4",
        "1.8.1-4ubuntu1.fips.2.5"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.5-5ubuntu1.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.5-5ubuntu1.1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.5-5ubuntu1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.8.4-5ubuntu2",
        "1.8.5-3ubuntu1",
        "1.8.5-5ubuntu1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.5-5ubuntu1.fips.1.1"
          },
          {
            "binary_name": "libgcrypt20-hmac",
            "binary_version": "1.8.5-5ubuntu1.fips.1.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:FIPS-updates:20.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.5-5ubuntu1.fips.1.1?arch=source\u0026distro=fips-updates/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.5-5ubuntu1.fips.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": []
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.5-5ubuntu1.fips.1.1"
          },
          {
            "binary_name": "libgcrypt20-hmac",
            "binary_version": "1.8.5-5ubuntu1.fips.1.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:FIPS:20.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.5-5ubuntu1.fips.1.1?arch=source\u0026distro=fips/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.5-5ubuntu1.fips.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": []
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libgcrypt20",
            "binary_version": "1.8.7-5ubuntu2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "libgcrypt20",
        "purl": "pkg:deb/ubuntu/libgcrypt20@1.8.7-5ubuntu2?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.7-5ubuntu2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [],
  "details": "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\u0027s public key, the generator defined by the receiver\u0027s public key, and the sender\u0027s ephemeral exponents can lead to a cross-configuration attack against OpenPGP.",
  "id": "UBUNTU-CVE-2021-40528",
  "modified": "2026-04-22T07:40:09Z",
  "published": "2021-09-06T19:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-40528"
    },
    {
      "type": "REPORT",
      "url": "https://eprint.iacr.org/2021/923"
    },
    {
      "type": "REPORT",
      "url": "https://ibm.github.io/system-security-research-updates/2021/07/20/insecurity-elgamal-pt1"
    },
    {
      "type": "REPORT",
      "url": "https://ibm.github.io/system-security-research-updates/2021/09/06/insecurity-elgamal-pt2"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-5080-1"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-5080-2"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2021-40528"
    }
  ],
  "related": [
    "USN-5080-1",
    "USN-5080-2"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2021-40528"
  ]
}



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Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.