CVE-2025-61672
Synapse: Invalid device keys degrade federation functionality
- State
- Published
- Severity
- 5.3 Medium
- Published
- Oct 8, 2025
- Updated
- Oct 15, 2025
- Reserved
- Sep 29, 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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N | GitHub_M |
Weaknesses
- CWE-1287 Improper Validation of Specified Type of Input
Affected Products
| Product | Versions |
|---|---|
synapseelement-hq |
|
References
- https://github.com/element-hq/synapse/security/advisories/GHSA-fh66-fcv5-jjfr
- https://github.com/element-hq/synapse/pull/17097
- https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1
- https://github.com/element-hq/synapse/commit/7069636c2d6d1ef2022287addf3ed8b919ef2740
- https://github.com/element-hq/synapse/releases/tag/v1.138.3
- https://github.com/element-hq/synapse/releases/tag/v1.139.1
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