CVE-2025-61672
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.
- CVSS 4.0
- 5.3
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 - EPSS
- 0.5% chance of exploitation in the next 30 days; higher than 40% of CVEs (scores of 2026-10-25)
- CWE
- CWE-1287
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-fh66-fcv5-jjfr | PyPI | matrix-synapse | <1.138.3 | 1.138.3 |
| GHSA-fh66-fcv5-jjfr | PyPI | matrix-synapse | >=1.139.0rc2 <1.139.1 | 1.139.1 |
| PYSEC-2026-1612 | PyPI | matrix-synapse | <1.138.3 >=1.139.0rc2 <1.139.1 | 1.138.3, 1.139.1 |
References
- https://github.com/element-hq/synapse/commit/26aaaf9e48fff80cf67a20c691c75d670034b3c1
- https://github.com/element-hq/synapse/commit/7069636c2d6d1ef2022287addf3ed8b919ef2740
- https://github.com/element-hq/synapse/pull/17097
- https://github.com/element-hq/synapse/releases/tag/v1.138.3
- https://github.com/element-hq/synapse/releases/tag/v1.139.1