# CVE-2025-30355: matrix-synapse: Synapse is an open source Matrix homeserver implementation

CVE-2025-30355 is fixed in matrix-synapse on 1 platform by DEBIAN-CVE-2025-30355 (version 1.121.0-6), released March 27, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-30355
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0123
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 27, 2025

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | matrix-synapse Debian 14 | 1.121.0-6 | [DEBIAN-CVE-2025-30355](https://patchblox.com/security/data/fix/linux/debian-cve-2025-30355.md) | Mar 27, 2025 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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