CVE-2023-32323 : Security Advisory and Response
Learn about CVE-2023-32323, a vulnerability in Synapse that allows disabling outgoing federation via malicious invites. Take immediate steps to upgrade Synapse for protection.
A detailed analysis of CVE-2023-32323 highlighting the vulnerability in Synapse's outgoing federation that can be exploited by sending malicious invites.
Understanding CVE-2023-32323
This section delves into the impact and technical details of the vulnerability.
What is CVE-2023-32323?
The CVE-2023-32323 vulnerability in Synapse allows a malicious user to disable outgoing federation to specific hosts by sending malicious invites. This can be exploited by users with permission to create certain state events on a Synapse homeserver.
The Impact of CVE-2023-32323
If successfully exploited, this vulnerability can result in the disruption of outbound federation from a particular Synapse homeserver to another, allowing an attacker to selectively disable communication.
Technical Details of CVE-2023-32323
This section provides insights into the vulnerability description, affected systems, and exploitation mechanism.
Vulnerability Description
In versions of Synapse up to and including 1.73, the 'invite_room_state' size was not limited, enabling the creation of excessively large invite events. However, Synapse 1.74 addresses this by restricting oversized 'invite_room_state' fields.
Affected Systems and Versions
The vulnerability affects Synapse versions older than 1.74.0, specifically impacting users who have not updated to the latest version.
Exploitation Mechanism
A malicious user with the ability to create certain state events can exploit this flaw by generating oversized 'invite_room_state' fields, thereby disabling outbound federation.
Mitigation and Prevention
In this section, we discuss immediate steps to take and long-term security practices to mitigate the risk posed by CVE-2023-32323.
Immediate Steps to Take
Server operators are strongly advised to upgrade to Synapse version 1.74 or newer promptly to prevent exploitation of this vulnerability.
Long-Term Security Practices
Regularly updating Synapse to the latest version ensures that security patches and fixes are applied promptly, reducing the risk of exploitation.
Patching and Updates
Stay informed about security advisories and promptly apply patches and updates released by Synapse to bolster the security of your homeserver infrastructure.