PYSEC-2026-664

    Dashboard / Vulnerabilities / PYSEC-2026-664

    PYSEC-2026-664

    Published: 2 Jul 2026Last Modified: 6 Jul 2026

    Summary: Matrix Synapse Security Filtering Flaw

    Details: The `on_get_missing_events` function in handlers/federation.py in Matrix Synapse before 0.31.1 has a security bug in the get_missing_events federation API where event visibility rules were not applied correctly.

    References: https://nvd.nist.gov/vuln/detail/CVE-2018-12291, https://github.com/matrix-org/synapse/pull/3371, https://github.com/matrix-org/synapse/commit/0834b49c6a9b6c597a154d4b2dfcf8fff90699ec, https://github.com/matrix-org/synapse, https://github.com/matrix-org/synapse/releases/tag/v0.31.1, https://pypi.org/project/matrix-synapse, https://github.com/advisories/GHSA-v8wm-g9f2-xjv4

    Affected packages

    Package

    Name: matrix-synapse

    Purl: pkg:pypi/matrix-synapse

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -0.31.1

    Affected versions

    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
    PYSEC-2026-664 | CVE-DB