Improper Validation of Specified Type of Input in Synapse - CVE-2025-61672
Published: April 23, 2026
Vulnerability identifier: #VU127007
CSH Severity: Low
CVSS v4: 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]
CVE-ID: CVE-2025-61672
CWE-ID: CWE-1287
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to degrade federation functionality.
The vulnerability exists due to improper validation of specified type of input in device key validation when processing device keys. A remote user can register and use invalid device keys to degrade federation functionality.
The issue can unpredictably break outbound federation to other homeservers.
Affected software
Synapse
How to mitigate CVE-2025-61672
Install security update from vendor's website.
Synapse - addressed in versions 1.138.3, 1.139.1