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

Source: https://junglewise.ai/threats/cve-2023-43796-synapse-vulnerable-to-leak-of-remote-user-device-information  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-10-31  
License: CC BY 4.0 with a link back

CVE-2023-43796 · Severity: low · CVSS 3.1 · Published 2023-10-31

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.

Technologies: [matrix-synapse (PyPI)](https://junglewise.ai/threats/technologies/matrix-synapse). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2023-43796 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-43796 being exploited in the wild.

**How severe is CVE-2023-43796?** Low severity, with a CVSS score of 3.1, published 31 October 2023.

**Which products and versions are affected?** matrix-synapse (PyPI) ECOSYSTEM:introduced=0,fixed=1.95.1, GIT:introduced=0,fixed=daec55e1fe120c564240c5386e77941372bf458f|ECOSYSTEM:introduced=0,fixed=1.95.1.

**Is there a fix for CVE-2023-43796?** Yes. matrix-synapse (PyPI): upgrade to 1.95.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2023-43796?** Check whether you run matrix-synapse (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- matrix-synapse (PyPI): upgrade to 1.95.1 or later

  ```sh
  pip install "matrix-synapse>=1.95.1"
  ```


## Affected products

- matrix-synapse (PyPI) ECOSYSTEM:introduced=0,fixed=1.95.1, GIT:introduced=0,fixed=daec55e1fe120c564240c5386e77941372bf458f|ECOSYSTEM:introduced=0,fixed=1.95.1

## Identifiers

- CVE-2023-43796
- GHSA-mp92-3jfm-3575
- PYSEC-2023-230

## Related threats

- [PYSEC-2026-2620 - matrix-sydent and matrix-synapse Use Cryptographically Weak PRNG](https://junglewise.ai/threats/cve-2019-11842-matrix-sydent-and-matrix-synapse-use-cryptographically-weak-prng)
- [PYSEC-2026-1614 - Synapse vulnerable to federation denial of service via malformed events](https://junglewise.ai/threats/cve-2025-30355-synapse-vulnerable-to-federation-denial-of-service-via-malformed)
- [PYSEC-2026-1610 - Synapse Matrix has a partial room state leak via Sliding Sync](https://junglewise.ai/threats/cve-2024-53867-synapse-matrix-has-a-partial-room-state-leak-via-sliding-sync)
- [Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders](https://junglewise.ai/threats/cve-2024-53863-synapse-can-be-forced-to-thumbnail-unexpected-file-formats)
- [PYSEC-2026-1611 - Synapse allows a a malformed invite to break the invitee's `/sync`](https://junglewise.ai/threats/cve-2024-52815-synapse-allows-a-a-malformed-invite-to-break-the-invitee-s-sync)