Executive Summary

This vulnerability affects Synapse, an open source Matrix homeserver implementation, in versions prior to 1.152.1. In federated rooms, malicious homeservers can craft specific room events that prevent Synapse from providing the full history of the room to clients who are paginating through messages.

As a result, clients may fail to display the complete room history. This issue is classified as a moderate severity vulnerability and has been fixed in Synapse version 1.152.1.

Useful 0 Not Useful 0

Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

Useful 0 Not Useful 0

Impact Analysis

The impact of this vulnerability is that clients using Synapse to access federated rooms may not be able to see the full history of messages in those rooms.

This can degrade the user experience by causing incomplete message histories to be displayed, potentially leading to confusion or loss of important context in conversations.

Useful 0 Not Useful 0

Detection Guidance

There are no specific detection commands or methods provided to identify this vulnerability on your network or system.

The vulnerability involves malicious homeservers crafting specific room events in federated rooms to disrupt Synapse's pagination of room history.

Since the issue affects Synapse versions prior to 1.152.1, checking the Synapse version in use can help detect if the system is vulnerable.

• Check Synapse version with a command like: synctl --version or by inspecting the installed package version.

Useful 0 Not Useful 0

Mitigation Strategies

The primary mitigation step is to upgrade Synapse to version 1.152.1 or later, where this vulnerability has been fixed.

There are no known workarounds for this issue, so applying the patch is essential.

Contacting security at element.io for further guidance is recommended if additional assistance is needed.

Useful 0 Not Useful 0