Improper access control in Synapse - CVE-2023-43796
Published: October 31, 2023 / Updated: May 4, 2026
Vulnerability identifier: #VU129610
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2023-43796
CWE-ID: CWE-284
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 attacker to disclose sensitive information.
The vulnerability exists due to improper access control in cached remote user device information handling when querying device information. A remote attacker can query cached device information of remote users to disclose sensitive information.
This can be used to enumerate remote users known to the homeserver.
How to mitigate CVE-2023-43796
Install security update from vendor's website.