CVE-2026-12199: Nltk Nltk/nltk

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Nltk Nltk/nltk: affected versions not specified

Published 2026-06-17. Last modified 2026-06-17.