CVE-2022-31152 : Vulnerability Insights and Analysis

A vulnerability has been identified in Synapse, an open-source Matrix homeserver maintained by the Matrix.org Foundation, allowing attackers to potentially cause divergence in room state between servers by crafting specially designed events.

Understanding CVE-2022-31152

This vulnerability arises due to the incorrect application of event authorization rules in versions of Synapse up to and including 1.61.0, which could lead to a denial of service (DoS) attack.

What is CVE-2022-31152?

Synapse, the affected Matrix homeserver, contains a flaw that allows attackers to create events that are accepted by Synapse but not by spec-conformant servers, impacting the room state consistency.

The Impact of CVE-2022-31152

The vulnerability poses a medium severity threat with a CVSS base score of 6.4. It has a high availability impact but low confidentiality and integrity impacts. The issue requires low privileges and no user interaction to exploit, making it a concern for systems with federation enabled.

Technical Details of CVE-2022-31152

Vulnerability Description

In Synapse versions up to and including 1.61.0, certain event authorization rules are not correctly enforced, potentially allowing the acceptance of non-compliant events, leading to possible divergence in room states.

Affected Systems and Versions

The vulnerability affects Synapse versions prior to 1.62.0.

Exploitation Mechanism

Attackers can exploit this vulnerability by crafting events that Synapse would accept but other spec-conformant servers would reject, causing inconsistencies in room states.

Mitigation and Prevention

Immediate Steps to Take

Administrators of Synapse homeservers with federation enabled are strongly advised to upgrade to version 1.62.0 or higher to mitigate this vulnerability. Additionally, federation can be disabled by setting

federation_domain_whitelist

to an empty list as a temporary workaround.

Long-Term Security Practices

Regularly monitor for security advisories and updates from the Matrix.org Foundation. Ensure timely installation of patches and updates to stay protected against known vulnerabilities.

Patching and Updates

Stay informed about the latest releases and security patches from Matrix.org to address security issues promptly and keep your systems secure.