UBUNTU-CVE-2021-4126

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    UBUNTU-CVE-2021-4126

    Published: 24 Dec 2021Last Modified: 22 Apr 2026
    Upstream:
    CVE-2021-4126

    Summary:

    Details: When receiving an OpenPGP/MIME signed email message that contains an additional outer MIME message layer, for example a message footer added by a mailing list gateway, Thunderbird only considered the inner signed message for the signature validity. This gave the false impression that the additional contents were also covered by the digital signature. Starting with Thunderbird version 91.4.1, only the signature that belongs to the top level MIME part will be considered for the displayed status. This vulnerability affects Thunderbird < 91.4.1.

    References: https://ubuntu.com/security/CVE-2021-4126, https://www.mozilla.org/en-US/security/advisories/mfsa2021-55/#CVE-2021-4126, https://ubuntu.com/security/notices/USN-5246-1, https://ubuntu.com/security/notices/USN-5248-1, https://www.cve.org/CVERecord?id=CVE-2021-4126

    Affected packages

    Package

    Name: thunderbird

    Purl: pkg:deb/ubuntu/thunderbird@1:91.5.0+build1-0ubuntu0.18.04.1?arch=source&distro=bionic

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -1:91.5.0+build1-0ubuntu0.18.04.1

    Affected versions

    1:52.4.0+build1-0ubuntu2

    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-2021-4126 | CVE-DB