CVE-2021-29431

    Dashboard / Vulnerabilities / CVE-2021-29431

    CVE-2021-29431

    Published: 15 Apr 2021Last Modified: 9 Jul 2026

    Summary:

    Details: Sydent is a reference Matrix identity server. Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting. It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration. This issue has been addressed in in 9e57334, 8936925, 3d531ed, 0f00412. A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.

    References: https://github.com/matrix-org/sydent/releases/tag/v2.3.0, https://github.com/matrix-org/sydent/commit/0f00412017f25619bc36c264b29ea96808bf310a, https://github.com/matrix-org/sydent/commit/3d531ed50d2fd41ac387f36d44d3fb2c62dd22d3, https://github.com/matrix-org/sydent/commit/8936925f561b0c352c2fa922d5097d7245aad00a, https://github.com/matrix-org/sydent/commit/9e573348d81df8191bbe8c266c01999c9d57cd5f, https://github.com/matrix-org/sydent/security/advisories/GHSA-9jhm-8m8c-c3f4, https://pypi.org/project/matrix-sydent/

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 0
    Fixed -c2ab10897500dbba1c0d4be33f42985d81bbad7d

    Affected versions

    fosdem_2021-01-15

    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
    CVE-2021-29431 | CVE-DB