CVE-2025-30355 — Improper Input Validation in Synapse

CWE-20 — Improper Input Validation7 documents6 sources
Severity
7.5HIGHNVD
CNA7.1VulnCheck7.1
EPSS
7.5%
top 8.16%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Element-hq SynapseMatrix Synapse
Timeline
PublishedMar 27

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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitability: 3.9 | Impact: 3.6

Affected Packages2 packages

▶NVDmatrix/synapse< 1.127.1
▶CVEListV5element-hq/synapse< 1.127.1

Patches

Patch: github.com ↗

🔴Vulnerability Details

5
GHSA
Synapse vulnerable to federation denial of service via malformed events↗2025-03-27
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OSV
CVE-2025-30355: Synapse is an open source Matrix homeserver implementation↗2025-03-27
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CVEList
Synapse vulnerable to federation denial of service via malformed events↗2025-03-27
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OSV
Synapse vulnerable to federation denial of service via malformed events↗2025-03-27
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VulnCheck
matrix synapse Improper Input Validation↗2025
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📋Vendor Advisories

1
Debian
CVE-2025-30355: matrix-synapse - Synapse is an open source Matrix homeserver implementation. A malicious server c...↗2025
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CVE-2025-30355 — Improper Input Validation in Synapse | cvebase