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GHSA-v56r-hwv5-mxg6

Synapse vulnerable to federation denial of service via malformed events

Source: GitHub Advisory Database (reviewed) High CVE-2025-30355

Packages

EcosystemPackageAffectedFixed in
PyPI matrix-synapse < 1.127.1 1.127.1

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact A malicious server can craft events with a `depth` outside the integer range allowed by Canonical JSON. When such an event is received by Synapse version up to 1.127.0, it prevents it from federating with other servers. The vulnerability has been exploited in the wild. ### Patches Fixed in Synapse v1.127.1. ### Workarounds Closed federation environments of trusted servers or non-federating installations are not affected. ### For more information If you have any questions or comments about this advisory, please email us at [security at element.io](mailto:[email protected]).

References

External links from the advisory. They lead to third-party sites.