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MEDIUM severity

Synapse vulnerable to leak of remote user device informationGHSA-mp92-3jfm-3575

MEDIUMFix: matrix-org/synapse@daec55e

GHSA-mp92-3jfm-3575 is a medium-severity (CVSS 5.3) Information Exposure vulnerability in matrix-synapse. A fix is available for matrix-synapse — see the affected versions and patch details below.

Also known asCVE-2023-43796PYSEC-2023-230
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk
0.00%0.57%1.13%1.70%0.2%1.2%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍matrix-synapse

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

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 Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPImatrix-synapseall versions1.95.1pip install --upgrade 'matrix-synapse==1.95.1'

Affected Products

2 products · 3 configurations
OS
fedorafedoraproject
2 versions
3839
Application
synapsematrix
< 1.95.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for matrix-synapse, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update matrix-synapse to 1.95.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mp92-3jfm-3575 is resolved across your whole dependency graph.

  3. Workarounds

    Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Frequently Asked Questions

### Impact Cached device information of remote users can be queried from Synapse. This can be used to enumerate the remote users known to a homeserver. ### Patches System administrators are encouraged to upgrade to Synapse 1.95.1 as soon as possible. ### Workarounds The `federation_domain_whitelist` can be used to limit federation traffic with a homeserver.
O3 Security · Impact-Aware SCA

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Synapse vulnerable to leak of remote user device…