Home/CVE/Synapse before 1.52.0 with URL preview functionality enabled will attempt to generate URL previews for media stream URLs
CVE

CVE-2022-41952

Synapse before 1.52.0 with URL preview functionality enabled will attempt to generate URL previews for media stream URLs

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.

MEDIUM · CVSS 6.5 EPSS 0.00552
Schedule remediation
  • SSVC automatable: yes - attacks can be scripted at scale
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-400Uncontrolled Resource Consumption
CWE-772Missing Release of Resource after Effective Lifetime
▤

Affected Products & Versions

1
matrix synapse< 1.53.0
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Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
PyPI matrix-synapse MODERATE fixed in 1.53.0
▣

Scoring & Timeline

6.5
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD22 Nov 2022 · 04:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
yes
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

5
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/matrix-org/synapse/pull/11784PatchThird Party Advisory
https://github.com/matrix-org/synapse/pull/11936PatchThird Party Advisory
https://github.com/matrix-org/synapse/releases/tag/v1.52.0Release NotesThird Party Advisory
https://github.com/matrix-org/synapse/releases/tag/v1.53.0Release NotesThird Party Advisory
https://github.com/matrix-org/synapse/security/advisories/GHSA-4822-jvwx-w47hMitigationThird Party Advisory
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