---
id: CVE-2018-1000164
aliases:
  - GHSA-32pc-xphx-q4f6
  - PYSEC-2018-55
title: Gunicorn contains Improper Neutralization of CRLF sequences in HTTP headers
summary: Gunicorn contains Improper Neutralization of CRLF sequences in HTTP headers
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: gunicorn
product: gunicorn
ecosystem: pip
affected:
  - gunicorn < 19.5.0
patched:
  - gunicorn 19.5.0
published: '2018-07-12'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T15:46:56.599254Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-32pc-xphx-q4f6'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2018-1000164'
  - url: 'https://github.com/benoitc/gunicorn/issues/1227'
  - url: >-
      https://github.com/benoitc/gunicorn/commit/1e10a02e73c87dfadc394b361af33864d0e59e24
  - url: >-
      https://epadillas.github.io/2018/04/02/http-header-splitting-in-gunicorn-19.4.5
  - url: 'https://github.com/benoitc/gunicorn'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/gunicorn/PYSEC-2018-55.yaml
  - url: 'https://lists.debian.org/debian-lts-announce/2018/04/msg00022.html'
  - url: 'https://usn.ubuntu.com/4022-1'
  - url: 'https://www.debian.org/security/2018/dsa-4186'
  - url: 'https://github.com/advisories/GHSA-32pc-xphx-q4f6'
tags:
  - osv
  - pip
  - ghsa
epss: 0.02414
epssPercentile: 0.83404
cwe:
  - CWE-93
ingestedAt: '2026-09-08T16:34:19.230Z'
---

## Overview

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.

## Affected packages

- `gunicorn < 19.5.0`

## Remediation

Upgrade to a patched release:

- `gunicorn 19.5.0`