Resource exhaustion in Synapse - CVE-2026-45078
Published: May 12, 2026
Vulnerability identifier: #VU131157
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-45078
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Matrix.org
Affected software:
Synapse
Synapse
Detailed vulnerability description
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in request processing when handling authenticated user requests. A local user can send requests that starve other requests of CPU to cause a denial of service.
Homeservers that trust all their local users are not at risk.
How to mitigate CVE-2026-45078
Install security update from vendor's website.