CVE-2019-18835: Matrix Synapse Signature Checking Vulnerability
Summary
CVE-2019-18835: Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs. Affects matrix-synapse versions < 1.5.0. Fixed in 1.5.0. How to fix ↓
Also tracked for
- matrix-synapse · Debian:13
The same CVE-2019-18835 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 for the Matrix protocol, which enables secure and decentralized communication. It provides a platform for real-time messaging, file sharing, and voice/video calling. The vulnerability in Matrix Synapse versions prior to 1.5.0 involves mishandling signature checking on certain federation APIs. Specifically, events sent over the /send_join, /send_leave, and /invite endpoints may not be correctly signed or may not originate from the expected servers.
Vulnerability Detail
The vulnerability arises due to a lack of proper signature verification on federation APIs in Matrix Synapse. This can lead to various security issues, such as unauthorized access, data tampering, and impersonation attacks. Attackers could exploit this vulnerability to send malicious events that appear legitimate, potentially compromising the integrity and security of the Matrix Synapse server and its federated communication network.
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
1.5.0
This is the first release that contains the fix.
pip install --upgrade "matrix-synapse==1.5.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no specific workaround provided for this vulnerability. It is crucial to apply the recommended fix by upgrading to Matrix Synapse version 1.5.0 or later.
Conclusion
The Matrix Synapse Signature Checking Vulnerability (CVE-2019-18835) affects versions prior to 1.5.0. It is crucial to upgrade to the latest version to address this vulnerability and ensure the integrity and security of Matrix Synapse servers. For further support and assistance in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for matrix-synapse →
FAQ
Matrix Synapse is an open-source server for the Matrix protocol, enabling secure and decentralized communication.
The vulnerability allows for potential unauthorized access, data tampering, and impersonation attacks on Matrix Synapse servers.
To fix this vulnerability, upgrade Matrix Synapse to version 1.5.0 or later.
No specific workarounds are provided. It is essential to apply the recommended fix by upgrading the software.
For more information, refer to the official advisory: [link to advisory]
References
Related vulnerabilities
Recent vulnerabilities recorded for matrix-synapse.
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