CVE-2018-12423: Matrix Synapse Authorization Error
Summary
CVE-2018-12423: Matrix Synapse Authorization Error. Affects matrix-synapse versions < 0.31.2. Fixed in 0.31.2. How to fix ↓
Also tracked for
- matrix-synapse · Debian:13
The same CVE-2018-12423 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 messaging protocol and server implementation that enables secure communication and collaboration. It provides a decentralized and federated network for real-time communication. The vulnerability identified as CVE-2018-12423 affects versions prior to 0.31.2 of the matrix-synapse package available on PyPI. This vulnerability allows unauthorized users to hijack rooms in the absence of an m.room.power_levels event.
Vulnerability Detail
The vulnerability arises from a lack of proper authorization checks in Synapse. When there is no m.room.power_levels event enforced, unauthenticated users can gain control over rooms. This can lead to unauthorized access, manipulation of room settings, and potential data breaches. The impact of this vulnerability is rated as HIGH with a CVSS score of 7.5.
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
0.31.2
This is the first release that contains the fix.
pip install --upgrade "matrix-synapse==0.31.2"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no specific workaround mentioned for this vulnerability. The recommended approach is to apply the fix by upgrading to the latest version of the matrix-synapse package.
Conclusion
The Matrix Synapse Authorization Error (CVE-2018-12423) is a high-severity vulnerability that allows unauthorized users to hijack rooms in the absence of proper authorization checks. Upgrading to version 0.31.2 or later of the matrix-synapse package is the recommended solution. For further support on vulnerability remediation, contact DevNack.com.
See every vulnerability recorded for matrix-synapse →
FAQ
Matrix Synapse is an open-source messaging protocol and server implementation that enables secure communication and collaboration.
The vulnerability allows unauthorized users to hijack rooms, potentially leading to unauthorized access, manipulation of room settings, and data breaches.
To fix this vulnerability, upgrade to version 0.31.2 or later of the matrix-synapse package.
There is no specific workaround mentioned for this vulnerability. It is recommended to upgrade to the latest version of the matrix-synapse package.
The CVSS score of this vulnerability is 7.5, indicating a high severity.
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