Resource exhaustion in Synapse - #VU139992
Published: July 29, 2026
Vulnerability identifier: #VU139992
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: N/A
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Affected software:
Synapse
Synapse
Detailed vulnerability description
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in user-configured push rules when processing or loading push rules. A remote user can create an unbounded number of push rules with an unbounded total size to cause a denial of service.
Homeservers that trust all their local users are not affected.
Remediation
Install security update from vendor's website.