# CVE-2018-12423: matrix-synapse: In Synapse before 0.31.2, unauthorised users can hijack rooms when there is no m.room.power_levels event in force.

CVE-2018-12423 is fixed in matrix-synapse on 1 platform by matrix-synapse 0.24.0+dfsg-1ubuntu0.1~esm1 (version 0.24.0+dfsg-1ubuntu0.1~esm1), released November 7, 2019. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2018-12423
- Priority: Routine
- CVSS: n/a (Low)
- EPSS: 0.0181
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 14, 2018

## Description

In Synapse before 0.31.2, unauthorised users can hijack rooms when there is no m.room.power_levels event in force.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | matrix-synapse Ubuntu 18.04.6 LTS (bionic) | 0.24.0+dfsg-1ubuntu0.1~esm1 | [matrix-synapse 0.24.0+dfsg-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-matrix-synapse-0.24.0-dfsg-1ubuntu0.1-esm1.md) | Nov 7, 2019 |

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Data as of 2026-11-07T12:40:37Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo