Advisory Weakness Curation

Denial of service due to incorrect application of event authorization rules ### Impact The Matrix specification specifies a list of event authorization rules https://spec.matrix.org/v1.3/rooms/v10/#authorization-rules which must be checked when determining if an event should be accepted into a room. In versions of Synapse up to and including v1.61, some of these rules are not correctly applied. An attacker could craft events which would be accepted by Synapse but not a spec-conformant server, potentially causing divergence in the room state between servers. ### Patches Administrators of homeservers with federation enabled are advised to upgrade to v1.62.0 or higher. ### Workarounds * Federation can be disabled by setting `federation_domain_whitelist` https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#federation_domain_whitelist to an empty list (`[]`). ### References * https://github.com/matrix-org/synapse/pull/13087 * https://github.com/matrix-org/synapse/pull/13088 ### For more information If you have any questions or comments about this advisory, e-mail us at [security@matrix.org](mailto:security@matrix.org).

Denial of service due to incorrect application of event authorization rules The Matrix specification specifies a list of event authorization rules https://spec.matrix.org/v1.3/rooms/v10/#authorization-rules which must be checked when determining if an event should be accepted into a room. In versions of Synapse up to and including v1.61, some of these rules are not correctly applied. An attacker could craft events which would be accepted by Synapse but not a spec-conformant server, potentially causing divergence in the room state between servers.

Duplicate This advisory duplicates another.