PYSEC-2026-1610
Synapse Matrix has a partial room state leak via Sliding Sync
Quick fix
PYSEC-2026-1610 — matrix-synapse: upgrade to the fixed version with the command below.
pip install --upgrade 'matrix-synapse>=1.120.1'Details
### Impact The Sliding Sync feature on Synapse versions between 1.113.0rc1 and 1.120.0 can leak partial room state changes to users no longer in a room. Non-state events, like messages, are unaffected.
### Patches Synapse version 1.120.1 fixes the problem.
### Workarounds Disable Sliding Sync.
### References https://github.com/matrix-org/matrix-spec-proposals/pull/4186 https://github.com/element-hq/synapse/blob/d80cd57c54427687afcb48740d99219c88a0fff1/synapse/config/experimental.py#L341-L344
### For more information
If you have any questions or comments about this advisory, please email us at [security at element.io](mailto:security@element.io).
Are you affected?
Enter the version of the package you're using.
Affected packages
1.113.0rc1Fixed in: 1.120.1pip install --upgrade 'matrix-synapse>=1.120.1'References
- https://github.com/element-hq/synapse/security/advisories/GHSA-56w4-5538-8v8h[WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2024-53867[ADVISORY]
- https://github.com/matrix-org/matrix-spec-proposals/pull/4186[WEB]
- https://github.com/element-hq/synapse[PACKAGE]
- https://pypi.org/project/matrix-synapse[PACKAGE]
- https://github.com/advisories/GHSA-56w4-5538-8v8h[ADVISORY]