---
id: CVE-2018-12423
aliases:
  - GHSA-ch5v-fhg8-7gv9
  - PYSEC-2026-844
title: Matrix Synapse Authorization Error
summary: Matrix Synapse Authorization Error
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
vendor: matrix-synapse
product: matrix-synapse
ecosystem: pip
affected:
  - matrix-synapse < 0.31.2
patched:
  - matrix-synapse 0.31.2
published: '2022-05-13'
updated: '2026-07-07'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-ch5v-fhg8-7gv9'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2018-12423'
  - url: 'https://github.com/matrix-org/matrix-doc/issues/1304'
  - url: 'https://bugs.debian.org/901549'
  - url: 'https://github.com/matrix-org/synapse'
  - url: 'https://matrix.org/blog/2018/06/14/security-update-synapse-0-31-2'
tags:
  - osv
  - pip
epss: 0.01816
epssPercentile: 0.77403
ingestedAt: '2026-07-08T18:25:48.386Z'
---

## Overview

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

## Affected packages

- `matrix-synapse < 0.31.2`

## Remediation

Upgrade to a patched release:

- `matrix-synapse 0.31.2`