Uncontrolled Resource Consumption in Matrix Synapse

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2022-41952: 0.94% estimated exploitation activity in the next 30 days; percentile 60.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Synapse before 1.52.0 with URL preview functionality enabled will attempt to generate URL previews for media stream URLs without properly limiting connection time. Connections will only be terminated after maxspidersize (default: 10M) bytes have been downloaded, which can in some cases lead to long-lived connections towards the streaming media server (for instance, Icecast). This can cause excessive traffic and connections toward such servers if their stream URL is, for example, posted to a large room with many Synapse instances with URL preview enabled. Patches 1.52.0 implements a timeout mechanism which will terminate URL preview connections after 30 seconds. Since generating URL previews for media streams is not supported and always fails, 1.53.0 additionally implements an allow list for content types for which Synapse will even attempt to generate a URL preview. We recommend upgrading to 1.53.0 to fully resolve the issue. Workarounds Turn off URL preview functionality by…

Published by the source

1 Apr 2022, 18:16 UTC

Last modified by the source

6 Jul 2026, 08:11 UTC

Source last checked

26 Oct 2026, 13:11 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4822-jvwx-w47h

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4822-jvwx-w47h

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# Patch Next advisory brief: CVE-2022-41952

Advisory: Uncontrolled Resource Consumption in Matrix Synapse
IDs: CVE-2022-41952, GHSA-4822-jvwx-w47h
Record: https://patchnext.com/advisories/cve-2022-41952 (revision 2, source checked 26 Oct 2026, 13:11 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: matrix-synapse 1.53.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI matrix-synapse: affected < 1.53.0; fixed in 1.53.0

## Suggested inspection (read-only)
- `python -m pip show matrix-synapse`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on matrix-synapse.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-4822-jvwx-w47h (OSV record GHSA-4822-jvwx-w47h lists affected ranges: PyPI matrix-synapse >=0 <1.53.0 (fixed))
- Verified: https://github.com/advisories/GHSA-4822-jvwx-w47h (GitHub-reviewed advisory GHSA-4822-jvwx-w47h lists affected ranges: PyPI matrix-synapse >=0 <1.53.0)

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