Input validation error in Synapse - CVE-2023-45129
Published: October 10, 2023 / Updated: May 4, 2026
Vulnerability identifier: #VU129609
CSH Severity: Low
CVSS v4: 6.9 [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]
CVE-ID: CVE-2023-45129
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
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.
Affected software
Synapse
Gentoo Linux
Fedora
matrix-synapse
net-im/synapse
Gentoo Linux
Fedora
matrix-synapse
net-im/synapse
How to mitigate CVE-2023-45129
Install security update from vendor's website.
Synapse - update to 1.94.0
matrix-synapse - addressed in versions 1.80.0-7.fc37, 1.94.0-2.fc38, 1.94.0-2.fc39
net-im/synapse - update to 1.96.0
matrix-synapse - addressed in versions 1.80.0-7.fc37, 1.94.0-2.fc38, 1.94.0-2.fc39
net-im/synapse - update to 1.96.0