CVE-2024-53867: Matrix Synapse Partial Room State Leak via Sliding Sync
Summary
CVE-2024-53867: Synapse Matrix has a partial room state leak via Sliding Sync. Affects matrix-synapse versions >= 1.113.0rc1, < 1.120.1. Fixed in 1.120.1. How to fix ↓
Also tracked for
- matrix-synapse · Debian:13
The same CVE-2024-53867 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Matrix Synapse is an open-source server implementation of the Matrix protocol, enabling real-time communication and collaboration. It is designed to facilitate secure and decentralized messaging, allowing users to create and manage rooms for discussions. The Sliding Sync feature enhances the user experience by providing efficient updates to room states. However, a vulnerability in versions 1.113.0rc1 to 1.120.0 has been identified, which can lead to unintended exposure of room state changes to users who are no longer part of the room.
Vulnerability Detail
The vulnerability arises from the Sliding Sync feature in Matrix Synapse, which, in specific versions, can leak partial room state changes to users who have left the room. This means that sensitive information about the room's state could be exposed to unauthorized users, potentially compromising privacy and security. Non-state events, such as messages, remain unaffected. The issue is classified under CWE-497, indicating a potential exposure of sensitive information.
How To Fix
Latest published version: 1.163.0 as of 22 Oct 2026
pip install --upgrade "matrix-synapse==1.163.0"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
1.120.1
This is the first release that contains the fix.
pip install --upgrade "matrix-synapse==1.120.1"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary measure, users can disable the Sliding Sync feature to prevent any potential leaks of room state changes. This can be done by modifying the configuration settings in the Synapse configuration file, typically located at /etc/matrix-synapse/homeserver.yaml, and setting enable_sliding_sync: false.
Conclusion
The identified vulnerability in Matrix Synapse poses a risk of leaking sensitive room state information to unauthorized users through the Sliding Sync feature. It is crucial for users to update to the patched version 1.120.1 or disable the feature to mitigate this risk. Regular monitoring for vulnerabilities, such as through tools like Vulert, can help maintain the security of your applications.
See every vulnerability recorded for matrix-synapse →
FAQ
Sliding Sync is a feature that allows for efficient updates of room states in real-time, enhancing the user experience by providing timely notifications of changes.
The vulnerability affects Matrix Synapse versions between 1.113.0rc1 and 1.120.0.
The vulnerability can leak partial room state changes, which may include sensitive information about the room's configuration and participants.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
The CVSS score of this vulnerability is 4.3, indicating a moderate level of severity.
References
Related vulnerabilities
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