CVE-2023-45129

matrix-synapse vulnerable to denial of service due to malicious server ACL events

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.

Category

4.9
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 0.25%
Vendor Advisory github.com Vendor Advisory github.com
Affected: matrix-org synapse
Published at:
Updated at:

References

Link Tags
https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4 vendor advisory
https://github.com/matrix-org/synapse/pull/16360 patch vendor advisory
https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-version release notes
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WRO4MPQ6HOXIUZM6RJP6VTCTMV7RD2T3/ mailing list
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KEVRB4MG5UXQ5RLZHSUJXM5GWEBYYS5B/ mailing list
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N6P4QULVUE254WI7XF2LWWOGHCYVFXFY/
https://security.gentoo.org/glsa/202401-12

Frequently Asked Questions

What is the severity of CVE-2023-45129?
CVE-2023-45129 has been scored as a medium severity vulnerability.
How to fix CVE-2023-45129?
To fix CVE-2023-45129, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2023-45129 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2023-45129 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2023-45129?
CVE-2023-45129 affects matrix-org synapse.
This platform uses data from the NIST NVD, MITRE CVE, MITRE CWE, First.org and CISA KEV but is not endorsed or certified by these entities. CVE is a registred trademark of the MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. CWE is a registred trademark of the MITRE Corporation and the authoritative source of CWE content is MITRE's CWE web site.
© 2025 Under My Watch. All Rights Reserved.