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CVE-2022-41952

Uncontrolled Resource Consumption in Matrix Synapse

MEDIUM
5.3
CVSS Score
Published: November 22, 2022 at 12:00 AM UTC
Updated: June 17, 2026 at 05:04 AM UTC
2 products affected across 2 vendorsSynapseSynapse

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.9%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Synapse· Matrixpypi
95%
v < 1.53.0
Affected range stops below 1.53.0, so it looks safe — our inference, not a vendor statement
Synapse· Matrix Orgpypi
60%
v < 1.53.0
Affected range stops below 1.53.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

PatchThird Party Advisory
Source: [email protected]
https://github.com/matrix-org/synapse/pull/11784
PatchThird Party Advisory
Source: [email protected]
https://github.com/matrix-org/synapse/pull/11936
Release NotesThird Party Advisory
Source: [email protected]
https://github.com/matrix-org/synapse/releases/tag/v1.52.0
Release NotesThird Party Advisory
Source: [email protected]
https://github.com/matrix-org/synapse/releases/tag/v1.53.0
MitigationThird Party Advisory
Source: [email protected]
https://github.com/matrix-org/synapse/security/advisories/GHSA-4822-jvwx-w47h

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.3MEDIUM[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-400CWE-772

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