CVE-2025-30355
HIGH7.1EPSS 13.2%Synapse vulnerable to federation denial of service via malformed events
Published: 3/27/2025Modified: 5/20/2026
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.
Affected packages (2)
- Debian/matrix-synapsefrom 0, < 1.121.0-6
- PyPI/matrix-synapsefrom 0, < 1.127.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H |
References (6)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2025-30355
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2025-30355
- PATCHhttps://github.com/element-hq/synapse
- WEBhttps://github.com/element-hq/synapse/commit/2277df2a1eb685f85040ef98fa21d41aa4cdd389
- WEBhttps://github.com/element-hq/synapse/releases/tag/v1.127.1
- WEBhttps://github.com/element-hq/synapse/security/advisories/GHSA-v56r-hwv5-mxg6