How severe is CVE-2019-11236?

CVE-2019-11236 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2019-11236?

CVE-2019-11236 affects the following packages: urllib3 (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2019-11236?

Update urllib3 to 1.24.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-11236 is resolved across your whole dependency graph.

How do I detect CVE-2019-11236 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for urllib3, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2019-11236 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2019-11236 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2019-11236, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2019-11236?

CVE-2019-11236 has an EPSS (Exploit Prediction Scoring System) score of 2.1%, placing it in the 82th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2019-11236?

CVE-2019-11236 is classified as CWE-93 (CWE-93). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2019-11236 published, and has it been updated?

CVE-2019-11236 was published on April 15, 2019 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

MEDIUM severity

CVE-2019-11236 — urllib3

MEDIUM

CVE-2019-11236 is a medium-severity (CVSS 6.1) CWE-93 vulnerability in urllib3. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for urllib3 — see the affected versions and patch details below.

Improper Neutralization of CRLF Sequences in urllib3 library for Python

Also known asGHSA-r64q-w8jr-g9qpPYSEC-2019-132

Published

Apr 15, 2019

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

2.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs82th percentile — riskier than 82% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐍urllib3

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

In the urllib3 library through 1.24.1 for Python, CRLF injection is possible if the attacker controls the request parameter.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`urllib3`	all versions	1.24.3`pip install --upgrade 'urllib3==1.24.3'`

Affected Products

1 product · 1 configurations

Application

urllib3python

≤ 1.24.2

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In the urllib3 library through 1.24.1 for Python, CRLF injection is poss…

github.comNVDJun 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for urllib3, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update urllib3 to 1.24.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-11236 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This issue affects the version of python-urllib3 shipped with Red Hat Gluster Storage 3, as it is vulnerable to CRLF injection. Red Hat Satellite 6.2 is on Maintenance Support 2 phase, hence only selected critical and important issues will be fixed. Please refer to Red Hat Satellite Product Life Cycle page for more…

Product	Fixed in	Advisory
Red Hat Ansible Tower 3.5 for RHEL 7	`ansible-tower-35/ansible-tower:3.5.6-1`	RHBA-2020:1539
Red Hat Ansible Tower 3.6 for RHEL 7	`ansible-tower-36/ansible-tower:3.6.4-1`	RHBA-2020:1540
Red Hat Enterprise Linux 7	`python-urllib3-0:1.10.2-7.el7`	RHSA-2019:2272
Red Hat Enterprise Linux 7	`python-pip-0:9.0.3-7.el7_7`	RHSA-2020:0850
Red Hat Enterprise Linux 7	`python-virtualenv-0:15.1.0-4.el7_7`	RHSA-2020:0851
Red Hat Enterprise Linux 7	`python-pip-0:9.0.3-7.el7_8`	RHSA-2020:2068
Red Hat Enterprise Linux 7	`python-virtualenv-0:15.1.0-4.el7_8`	RHSA-2020:2081
Red Hat Enterprise Linux 8	`python27:2.7-8010020190903182548.51c94b97`	RHSA-2019:3335

Frequently Asked Questions

In the urllib3 library through 1.24.1 for Python, CRLF injection is possible if the attacker controls the request parameter.

O3 Security · Impact-Aware SCA

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