matrix-synapse vulnerable to denial of service due to malicious server ACL events
ImpactA malicious server ACL event can impact performance temporarily or permanently leading to a persistent denial of service.Homeservers running on a closed federation (which presumably do not need to use server ACLs) are not affected.PatchesServer administrators are advised to upgrade to Synapse 1.94.0 or later.WorkaroundsRooms with malicious server ACL events can be [purged and blocked](https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-version) using the admin API.