Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. The Matrix specification specifies a list of [event authorization rules](https://spec.matrix.org/v1.2/rooms/v9/#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 version 1.61.0, 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. Administrators of homeservers with federation enabled are advised to upgrade to version 1.62.0 or higher. 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 (`[]`) as a workaround.
The product does not properly anticipate or handle exceptional conditions that rarely occur during normal operation of the product.
The product does not handle or incorrectly handles an exceptional condition.
| Link | Tags |
|---|---|
| https://github.com/matrix-org/synapse/security/advisories/GHSA-jhjh-776m-4765 | issue tracking third party advisory mitigation |
| https://github.com/matrix-org/synapse/pull/13087 | issue tracking third party advisory patch |
| https://github.com/matrix-org/synapse/pull/13088 | issue tracking third party advisory patch |
| https://github.com/matrix-org/synapse/releases/tag/v1.62.0 | third party advisory release notes |