CVE-2023-32323
Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites
In short
A malicious user on a Matrix Synapse server can send specially crafted invitations to disable communication between that server and another server. This breaks federation, preventing legitimate message exchange between the two servers.
Technical detail
A local attacker with state event creation permissions can craft oversized `invite_room_state` fields in room invitations to trigger denial-of-service conditions that disable outbound federation to a targeted homeserver. Pre-conditions include federation enablement and attacker permissions; mitigation requires upgrading to Synapse 1.74+ to enforce size limits on invite event payloads.
Summary generated and translated by AI from the official description.
Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. A malicious user on a Synapse homeserver X with permission to create certain state events can disable outbound federation from X to an arbitrary homeserver Y. Synapse instances with federation disabled are not affected. In versions of Synapse up to and including 1.73, Synapse did not limit the size of `invite_room_state`, meaning that it was possible to create an arbitrarily large invite event. Synapse 1.74 refuses to create oversized `invite_room_state` fields. Server operators should upgrade to Synapse 1.74 or newer urgently.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L
Affected products
matrix-org · synapseWant to know if your infrastructure is exposed to this?
Talk to TrueHacking →References
https://github.com/matrix-org/synapse/issues/14492https://github.com/matrix-org/synapse/pull/14642https://github.com/matrix-org/synapse/security/advisories/GHSA-f3wc-3vxv-xmvrhttps://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UJIJRP5ZH6B3KGFLHCAKR2IX2Y4Z25QD/