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CVE-2025-30355

Synapse vulnerable to federation denial of service via malformed events

Published: Mar 27, 2025Updated: Aug 26, 2025 Sources: CVE List NVD GHSACWE-20
7.1HIGH
NVD MITRE
EPSS Score
1.1%
Top 39.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:NI:LA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:HAvailability
High
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Weaknesses

CWE-20NVD-CWE-noinfo

Affected Products

synapsematrix
On-premWeb App
Communications / messaging-chat
matrix-synapsePyPIOSS Libraries
synapseelement-hq
Mixed
Communications / messaging-chat
matrixoss-projectGBCommunicationsaka synapse, matrix irc bridge, javascript sdk
pypipackage-ecosystemOSS Libraries
element-hqoss-projectCommunications

Exploitability

Official Patch Available
No detection template yetWe can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Initial Access
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References

https://github.com/element-hq/synapse/commit/2277df2a1eb685f85040ef98fa21d41aa4cdd389
github.com
https://github.com/element-hq/synapse/releases/tag/v1.127.1
github.com
https://github.com/element-hq/synapse/security/advisories/GHSA-v56r-hwv5-mxg6
github.com
and 2 more references View all →

Timeline

Published
Mar 27, 2025
Last Updated
Aug 26, 2025

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