What is CVE-2022-41952?

CVE-2022-41952 is a medium-severity vulnerability in Matrix Synapse, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2022-11-22.

How severe is CVE-2022-41952?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Resource exhaustion in Matrix Synapse

CVE-2022-41952

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 `max_spider_size` (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. Version 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. Upgrade to 1.53.0 to fully resolve the issue. As a workaround, turn off URL preview functionality by setting `url_preview_enabled: false` in the Synapse configuration file.

Vulnerability class: DoS (Denial of Service)

Published 2022-11-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L.

EPSS exploit prediction

EPSS: 0.009 (58.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 58.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.009 · change: +0.001

Affected products

Matrix Synapse
Matrix-Org Synapse — versions < 1.53.0

Weakness classification (CWE)

References

github.com/matrix-org/synapse/security/advisories/GHSA-4822-jvwx-w47h (Third Party Advisory, Mitigation)
github.com/matrix-org/synapse/pull/11784 (Patch, Third Party Advisory)
github.com/matrix-org/synapse/pull/11936 (Patch, Third Party Advisory)
github.com/matrix-org/synapse/releases/tag/v1.52.0 (Third Party Advisory, Release Notes)
github.com/matrix-org/synapse/releases/tag/v1.53.0 (Third Party Advisory, Release Notes)

Frequently asked questions

What is CVE-2022-41952?: CVE-2022-41952 is a medium-severity vulnerability in Matrix Synapse, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2022-11-22.
How severe is CVE-2022-41952?: Medium severity. CVSS v3 base score is 6.5 out of 10.