CVE-2023-45129

Publication date 10 October 2023

Last updated 26 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
matrix-synapse	24.10 oracular	Not affected
	24.04 LTS noble	Not affected
	23.10 mantic	Ignored end of life, was needs-triage
	23.04 lunar	Ignored end of life, was needs-triage
	22.04 LTS jammy	Ignored patch infeasible
	20.04 LTS focal	Ignored end of standard support, was ignored [patch infeasible]
	18.04 LTS bionic	Ignored end of standard support
	16.04 LTS xenial	Not in release
	14.04 LTS trusty	Not in release

Notes

john-breton

Both rust/src and stubs/synapses (which the patch targets) DNE in bionic-jammy. Without that functionality, patching is infeasible, and those modules require significant revisions to even get to function with the older versions.

Severity score breakdown

CVSS version: CVSS v3.0

Base score 4.9 · Medium

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	High
User interaction	None
Scope	Unchanged
Confidentiality impact	None
Integrity impact	None
Availability impact	High

Scores

Parameter	Value
Base score	4.9 · Medium
Exploitability score	-
Impact score	-

Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H