Incorrect authorization in Synapse - CVE-2022-39374
Published: May 24, 2023 / Updated: May 4, 2026
Vulnerability identifier: #VU129606
CSH Severity: Low
CVSSv4.0: 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-2022-39374
CWE-ID: CWE-863
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
Synapse
Synapse
Software vendor:
Matrix.org
Matrix.org
Description
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to improper authorization in event authorization rules during state resolution when processing room state from a joined malicious homeserver. A remote user can trick Synapse into accepting previously rejected events to cause a denial of service.
Exploitation is possible only when the homeserver is joined to rooms that include or invite members of untrusted homeservers.
Remediation
Install security update from vendor's website.