CVE-2023-32323

Public Exploit
Synapse Outgoing federation to specific hosts can be disabled by sending malicious invites

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.

Category

5.0
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 0.13%
Vendor Advisory github.com
Affected: matrix-org synapse
Published at:
Updated at:

References

Link Tags
https://github.com/matrix-org/synapse/security/advisories/GHSA-f3wc-3vxv-xmvr mitigation vendor advisory
https://github.com/matrix-org/synapse/issues/14492 issue tracking exploit
https://github.com/matrix-org/synapse/pull/14642 patch
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UJIJRP5ZH6B3KGFLHCAKR2IX2Y4Z25QD/

Frequently Asked Questions

What is the severity of CVE-2023-32323?
CVE-2023-32323 has been scored as a medium severity vulnerability.
How to fix CVE-2023-32323?
To fix CVE-2023-32323, 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-2023-32323 being actively exploited in the wild?
It is possible that CVE-2023-32323 is being exploited or will be exploited in a near future based on public information. 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-2023-32323?
CVE-2023-32323 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.