# CVE-2023-42453: matrix-synapse: Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation

CVE-2023-42453 is fixed in matrix-synapse on 1 platform, first by DEBIAN-CVE-2023-42453, released September 27, 2023. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2023-42453
- Priority: Routine
- CVSS: 4.3 (medium)
- EPSS: 0.0078
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 27, 2023

## Description

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Users were able to forge read receipts for any event (if they knew the room ID and event ID). Note that the users were not able to view the events, but simply mark it as read. This could be confusing as clients will show the event as read by the user, even if they are not in the room. This issue has been patched in version 1.93.0. Users are advised to upgrade. There are no known workarounds for this issue.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | matrix-synapse Debian 14 | 1.93.0-1 | [DEBIAN-CVE-2023-42453](https://patchblox.com/security/data/fix/linux/debian-cve-2023-42453.md) | Sep 27, 2023 |
| Linux | matrix-synapse Ubuntu 22.04.1 LTS (jammy) | 1.53.0-1ubuntu0.1~esm2 | [matrix-synapse 1.53.0-1ubuntu0.1~esm2](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-matrix-synapse-1.53.0-1ubuntu0.1-esm2.md) | Dec 3, 2024 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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