medium
6.5
CWE
674
Advisory Published
Advisory Published
Updated

CVE-2022-31052: URL previews can crash Synapse media repositories or Synapse monoliths

First published: Tue Jun 28 2022(Updated: )

### Impact URL previews of some web pages can exhaust the available stack space for the Synapse process due to unbounded recursion. This is sometimes recoverable and leads to an error for the request causing the problem, but in other cases the Synapse process may crash altogether. It is possible to exploit this maliciously, either by malicious users on the homeserver, or by remote users sending URLs that a local user's client may automatically request a URL preview for. Remote users are not able to exploit this directly, because [the URL preview endpoint is authenticated](https://spec.matrix.org/v1.2/client-server-api/#get_matrixmediav3preview_url). ### Am I affected? * deployments with `url_preview_enabled: false` set in configuration are not affected. * deployments with `url_preview_enabled: true` set in configuration **are** affected. * deployments with no configuration value set for `url_preview_enabled` are not affected, because the default is `false`. ### Patches Administrators of homeservers with URL previews enabled are advised to upgrade to v1.61.1 or higher. ### Workarounds * URL previews can be disabled in the configuration file by setting `url_preview_enabled: false`. * Deployments using workers can choose to offload URL previews to one or more dedicated worker(s), ensuring that a process crash does not disrupt other functionality of Synapse. ### For more information If you have any questions or comments about this advisory, e-mail us at [security@matrix.org](mailto:security@matrix.org).

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

Affected SoftwareAffected VersionHow to fix
Matrix Synapse<1.61.1
Fedoraproject Fedora=35
Fedoraproject Fedora=36
pip/matrix-synapse<1.61.1
1.61.1

Remedy

https://github.com/matrix-org/synapse/commit/fa1308061802ac7b7d20e954ba7372c5ac292333

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Reference Links

Frequently Asked Questions

  • What is CVE-2022-31052?

    CVE-2022-31052 is a vulnerability in Synapse, an open source home server implementation for the Matrix chat network, that can cause stack exhaustion due to unbounded recursion in URL previews of certain web pages.

  • How does CVE-2022-31052 affect Synapse and Fedoraproject Fedora?

    CVE-2022-31052 affects Synapse versions prior to 1.61.1 and Fedoraproject Fedora versions 35 and 36.

  • What is the severity of CVE-2022-31052?

    CVE-2022-31052 has a severity level of medium, with a severity value of 6.5.

  • How can CVE-2022-31052 be exploited?

    CVE-2022-31052 can be exploited by sending requests with specially crafted URLs that trigger unbounded recursion in URL previews.

  • How do I fix CVE-2022-31052?

    To fix CVE-2022-31052, it is recommended to update to Synapse version 1.61.1 or later.

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