UBUNTU-CVE-2021-40528

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    UBUNTU-CVE-2021-40528

    Published: 6 Sept 2021Last Modified: 22 Apr 2026
    Upstream:
    CVE-2021-40528

    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.

    References: https://ubuntu.com/security/CVE-2021-40528, https://eprint.iacr.org/2021/923, https://ibm.github.io/system-security-research-updates/2021/07/20/insecurity-elgamal-pt1, https://ibm.github.io/system-security-research-updates/2021/09/06/insecurity-elgamal-pt2, https://ubuntu.com/security/notices/USN-5080-1, https://ubuntu.com/security/notices/USN-5080-2, https://www.cve.org/CVERecord?id=CVE-2021-40528

    Affected packages

    Package

    Name: libgcrypt20

    Purl: pkg:deb/ubuntu/[email protected]+esm1?arch=source&distro=esm-infra/xenial

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -1.6.5-2ubuntu0.6+esm1

    Affected 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

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    UBUNTU-CVE-2021-40528 | CVE-DB