high
7.5
CWE
22
Advisory Published
Advisory Published
Updated

CVE-2021-41281: Path traversal in Matrix Synapse

First published: Tue Nov 23 2021(Updated: )

### Impact Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory, potentially outside the media store directory. The last two directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers configured with a federation whitelist are also unaffected. ### Patches Server administrators should upgrade to 1.47.1 or later. ### Workarounds Server administrators using a reverse proxy could, at the expense of losing media functionality, block the following endpoints: * `/_matrix/media/r0/download/{serverName}/{mediaId}` * `/_matrix/media/r0/download/{serverName}/{mediaId}/{fileName}` * `/_matrix/media/r0/thumbnail/{serverName}/{mediaId}` Alternatively, non-containerized deployments can be adapted to use the hardened systemd config, located at `contrib/systemd/override-hardened.conf`. ### References n/a ### For more information If you have any questions or comments about this advisory, e-mail us at security@matrix.org.

Credit: security-advisories@github.com security-advisories@github.com

Affected SoftwareAffected VersionHow to fix
Matrix Synapse<1.47.1
Fedoraproject Fedora=34
Fedoraproject Fedora=35
pip/matrix-synapse<1.47.1
1.47.1
<1.47.1
=34
=35

Remedy

https://github.com/matrix-org/synapse/commit/91f2bd090

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Reference Links

Frequently Asked Questions

  • What is CVE-2021-41281?

    CVE-2021-41281 is a vulnerability in Synapse, a package for Matrix homeservers, which allows downloading a file from a remote server into an arbitrary directory without authentication.

  • How does CVE-2021-41281 affect Synapse instances with the media repository enabled?

    CVE-2021-41281 affects Synapse instances with the media repository enabled by allowing the download of a file from a remote server into any directory, regardless of authentication.

  • What is the severity of CVE-2021-41281?

    The severity of CVE-2021-41281 is high with a CVSS score of 7.5.

  • How can I fix CVE-2021-41281 in Synapse?

    To fix CVE-2021-41281 in Synapse, update to version 1.47.1 or later. Refer to the Synapse release notes and GitHub advisory for more information.

  • What is CWE-22?

    CWE-22 is a vulnerability category called Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), which is the category of vulnerability that CVE-2021-41281 falls under.

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