Impact A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 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.