What’s Vulnerable › Vulnerabilities
CVE-2023-43796: Synapse vulnerable to leak of remote user device information
- Severity: medium (CVSS 5.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.9% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2023-10-31 · updated 2026-06-17
- Weakness: CWE-200
Description
Synapse is an open-source Matrix homeserver Prior to versions 1.95.1 and 1.96.0rc1, cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. System administrators are encouraged to upgrade to Synapse 1.95.1 or 1.96.0rc1 to receive a patch. As a workaround, the `federation_domain_whitelist` can be used to limit federation traffic with a homeserver.
Affected products
- Fedoraproject Fedora: 38, 39
- matrix-org synapse: before 1.95.1 — fixed in 1.95.1
How to fix
Upgrade to a fixed version: matrix-org synapse 1.95.1. Check the vendor advisory for mitigations.
References
- https://github.com/matrix-org/synapse/commit/daec55e1fe120c564240c5386e77941372bf458f
- https://github.com/matrix-org/synapse/security/advisories/GHSA-mp92-3jfm-3575
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2IDEEZMFJBDLTFHQUTZRJJNCOZGQ2ZVS/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VH3RNC5ZPQZ4OKPSL4E6BBJSZOQLGDEY/
- https://security.gentoo.org/glsa/202401-12
- https://github.com/matrix-org/synapse/commit/daec55e1fe120c564240c5386e77941372bf458f
- https://github.com/matrix-org/synapse/security/advisories/GHSA-mp92-3jfm-3575
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2IDEEZMFJBDLTFHQUTZRJJNCOZGQ2ZVS/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VH3RNC5ZPQZ4OKPSL4E6BBJSZOQLGDEY/
- https://security.gentoo.org/glsa/202401-12
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