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.
https://security.gentoo.org/glsa/202401-12
https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-version
https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4
Published: 2023-10-10
Updated: 2024-01-07
Base Score: 6.1
Vector: CVSS2#AV:N/AC:L/Au:M/C:N/I:N/A:C
Severity: Medium
Base Score: 4.9
Vector: CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Severity: Medium
Base Score: 6.9
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Severity: Medium