Headline
GHSA-5chr-wjw5-3gq4: matrix-synapse vulnerable to denial of service due to malicious server ACL events
Impact
A 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.
Patches
Server administrators are advised to upgrade to Synapse 1.94.0 or later.
Workarounds
Rooms with malicious server ACL events can be purged and blocked using the admin API.
References
https://github.com/matrix-org/synapse/pull/16360
matrix-synapse vulnerable to denial of service due to malicious server ACL events
Moderate severity GitHub Reviewed Published Oct 10, 2023 in matrix-org/synapse • Updated Oct 10, 2023
Related news
Gentoo Linux Security Advisory 202401-12 - Multiple vulnerabilities have been found in Synapse, the worst of which could result in information leaks. Versions greater than or equal to 1.96.0 are affected.
Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Prior to version 1.94.0, a 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. Server administrators are advised to upgrade to Synapse 1.94.0 or later. As a workaround, rooms with malicious server ACL events can be purged and blocked using the admin API.