Improper Check for Unusual or Exceptional Conditions in Synapse - CVE-2026-45076
Published: May 12, 2026
Vulnerability identifier: #VU131158
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-45076
CWE-ID: CWE-754
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Matrix.org
Affected software:
Synapse
Synapse
Detailed vulnerability description
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to improper handling of crafted room events in pagination in federated room history pagination when processing room events from federated homeservers. A remote user can send specially crafted room events to cause a denial of service.
The issue can prevent paginating clients from receiving full room history and may cause clients to fail to display room history.
How to mitigate CVE-2026-45076
Install security update from vendor's website.