BIT-syncthing-2021-21404

    Dashboard / Vulnerabilities / BIT-syncthing-2021-21404

    BIT-syncthing-2021-21404

    Published: 24 Jul 2024Last Modified: 8 Sept 2026

    Summary: Crash due to malformed relay protocol message

    Details: Syncthing is a continuous file synchronization program. In Syncthing before version 1.15.0, the relay server `strelaysrv` can be caused to crash and exit by sending a relay message with a negative length field. Similarly, Syncthing itself can crash for the same reason if given a malformed message from a malicious relay server when attempting to join the relay. Relay joins are essentially random (from a subset of low latency relays) and Syncthing will by default restart when crashing, at which point it's likely to pick another non-malicious relay. This flaw is fixed in version 1.15.0.

    References: https://github.com/syncthing/syncthing/commit/fb4fdaf4c0a79c22cad000c42ac1394e3ccb6a97, https://github.com/syncthing/syncthing/releases/tag/v1.15.0, https://github.com/syncthing/syncthing/security/advisories/GHSA-x462-89pf-6r5h, https://pkg.go.dev/github.com/syncthing/syncthing, https://nvd.nist.gov/vuln/detail/CVE-2021-21404

    Affected packages

    Package

    Name: syncthing

    Purl: pkg:bitnami/syncthing

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 0
    Fixed -1.15.0

    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
    BIT-syncthing-2021-21404 | CVE-DB