# CVE-2025-61672: matrix-synapse: Synapse is an open source Matrix homeserver implementation

CVE-2025-61672 is fixed in matrix-synapse on 1 platform by DEBIAN-CVE-2025-61672 (version 1.139.2-1), released October 8, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-61672
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0048
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 8, 2025

## Description

Synapse is an open source Matrix homeserver implementation. Lack of validation for device keys in Synapse before 1.138.3 and in Synapse 1.139.0 allow an attacker registered on the victim homeserver to degrade federation functionality, unpredictably breaking outbound federation to other homeservers. The issue is patched in Synapse 1.138.3, 1.138.4, 1.139.1, and 1.139.2. Note that even though 1.138.3 and 1.139.1 fix the vulnerability, they inadvertently introduced an unrelated regression. For this reason, the maintainers of Synapse recommend skipping these releases and upgrading straight to 1.138.4 and 1.139.2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | matrix-synapse Debian 14 | 1.139.2-1 | [DEBIAN-CVE-2025-61672](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61672.md) | Oct 8, 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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