Summary
URL previews of unusual or maliciously-crafted pages can crash Synapse media repositories or Synapse monoliths
Am I affected?
- deployments with
url_preview_enabled: falseset in configuration are not affected. - deployments with
url_preview_enabled: trueset in configuration are affected. - deployments with no configuration value set for
url_preview_enabledare not affected, because the default isfalse.
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 [email protected].
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.
CVE-2022-31052 has a CVSS score of 6.5 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.61.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Administrators of homeservers with URL previews enabled are advised to upgrade to v1.61.1 or higher.
Frequently Asked Questions
- What is CVE-2022-31052? CVE-2022-31052 is a high-severity security vulnerability in matrix-synapse (pip), affecting versions < 1.61.1. It is fixed in 1.61.1.
- How severe is CVE-2022-31052? CVE-2022-31052 has a CVSS score of 6.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of matrix-synapse are affected by CVE-2022-31052? matrix-synapse (pip) versions < 1.61.1 is affected.
- Is there a fix for CVE-2022-31052? Yes. CVE-2022-31052 is fixed in 1.61.1. Upgrade to this version or later.
- Is CVE-2022-31052 exploitable, and should I be worried? Whether CVE-2022-31052 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2022-31052 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2022-31052? Upgrade
matrix-synapseto 1.61.1 or later.