Input validation error in Synapse - CVE-2023-45129
Published: October 10, 2023 / Updated: May 4, 2026
Vulnerability identifier: #VU129609
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2023-45129
CWE-ID: CWE-20
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 input validation in server ACL event handling when processing malicious server ACL events. A remote privileged user can send a malicious server ACL event to cause a denial of service.
Homeservers running on a closed federation are not affected.
How to mitigate CVE-2023-45129
Install security update from vendor's website.