CVE-2026-33231: Nltk

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

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.

Affected products

• Nltk Nltk: up to and including 3.9.3

Published 2026-03-20. Last modified 2026-09-09.