CVE-2023-42453: Open Source Vulnerability in matrix-synapse
Summary
CVE-2023-42453: Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Affects matrix-synapse versions >= 1.34.0, < 1.93.0. Fixed in 1.93.0. How to fix ↓
Also tracked for
- matrix-synapse · Debian:13
The same CVE-2023-42453 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 Matrix homeserver developed and maintained by the Matrix.org Foundation. It serves as a platform for Matrix communication, allowing users to create and join rooms, send messages, and interact with other users. The vulnerability identified in matrix-synapse allows users to forge read receipts for any event in a room, even if they are not present in the room. Although users cannot view the events, they can mark them as read, which may lead to confusion as clients will display the events as read by the user. This vulnerability has been addressed in version 1.93.0 of matrix-synapse. It is recommended that users upgrade to this version to mitigate the issue.
Vulnerability Detail
The vulnerability in matrix-synapse allows users to manipulate read receipts for events in a room by forging the room ID and event ID. While users cannot access the events themselves, they can mark them as read, causing clients to display the events as read by the user. This can lead to confusion and misrepresentation of the user's actual presence in the room. The vulnerability has a CVSS score of 4.3, indicating a moderate severity level. It was introduced in version 1.34.0 of matrix-synapse and has been fixed in version 1.93.0.
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
1.93.0
This is the first release that contains the fix.
pip install --upgrade "matrix-synapse==1.93.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Conclusion
The vulnerability in matrix-synapse allows users to forge read receipts for events in a room, potentially leading to confusion and misrepresentation of the user's presence. To mitigate this issue, users should upgrade to version 1.93.0 or later of matrix-synapse. For further support and assistance with vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for matrix-synapse →
FAQ
matrix-synapse is an open-source Matrix homeserver developed by the Matrix.org Foundation. It enables users to communicate via the Matrix protocol, creating and joining rooms, sending messages, and interacting with other users.
The vulnerability allows users to mark events as read in a room, even if they are not present in the room. This can lead to confusion as clients will display the events as read by the user, potentially misrepresenting their actual presence in the room.
To fix this vulnerability, users should upgrade their matrix-synapse installation to version 1.93.0 or later. This version includes the necessary patches to prevent users from forging read receipts for events.
There are no known workarounds for this vulnerability. Upgrading to the patched version is the recommended solution.
More information about this vulnerability can be found in the advisory database of the Python Package Index (PyPI) at the following source: https://github.com/pypa/advisory-database/blob/main/vulns/matrix-synapse/PYSEC-2023-180.yaml
References
Related vulnerabilities
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