CVE-2026-33231
Received Received - Intake
Unauthenticated Remote Shutdown Vulnerability in NLTK WordNet Server

Publication date: 2026-03-20

Last updated on: 2026-03-23

Assigner: GitHub, Inc.

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.
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Meta Information
Published
2026-03-20
Last Modified
2026-03-23
Generated
2026-06-16
AI Q&A
2026-03-21
EPSS Evaluated
2026-06-14
NVD
CVE-2026-33231
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
nltk nltk to 3.9.3 (inc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-306 The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
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Executive Summary

This vulnerability exists in the Natural Language Toolkit (NLTK) versions 3.9.3 and prior, specifically in the wordnet_app module. When the local WordNet Browser HTTP server is started in its default mode, an unauthenticated remote attacker can send a simple HTTP GET request with the path /SHUTDOWN%20THE%20SERVER. This request causes the server process to terminate immediately by calling os._exit(0), resulting in a denial of service.

Impact Analysis

The impact of this vulnerability is a denial of service (DoS). An attacker can remotely and without authentication shut down the local WordNet Browser HTTP server, causing it to stop functioning abruptly. This can disrupt any services or applications relying on this server, leading to potential downtime and loss of availability.

Compliance Impact

I don't know

Detection Guidance

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Mitigation Strategies

To mitigate this vulnerability, update NLTK to a version later than 3.9.3 where the issue has been patched (commit bbaae83db86a0f49e00f5b0db44a7254c268de9b).

Alternatively, avoid running the WordNet Browser HTTP server in its default mode or restrict access to it to trusted users only to prevent unauthenticated remote shutdown.

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