CVE-2025-30355

Synapse vulnerable to federation denial of service via malformed events

Published Mar 27, 2025 CVSS 3.1 · 7.1 High EPSS 1.2% KEV · Not listed
Description
Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wild and has been fixed in Synapse v1.127.1. No known workarounds are available.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2025-8265 Synapse vulnerable to federation denial of service via malformed events
Github GHSA Github GHSA GHSA-v56r-hwv5-mxg6 Synapse vulnerable to federation denial of service via malformed events
History
Type Values Removed Values Added
First Time appeared Matrix
Matrix synapse
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*
Vendors & Products Matrix
Matrix synapse
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wild and has been fixed in Synapse v1.127.1. No known workarounds are available.
Title Synapse vulnerable to federation denial of service via malformed events
Weaknesses CWE-20
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Mar 27, 2025, 1:47 PM
Reserved
Mar 21, 2025, 2:12 PM
Status
Analyzed
Published
Mar 27, 2025, 1:15 AM
Modified
Jun 17, 2026, 9:08 AM