NLTK WordNet Browser Unauthenticated Remote Denial-of-Service Vulnerability

A denial-of-service vulnerability has been identified in the NLTK (Natural Language Toolkit) WordNet Browser application, specifically in versions through 3.9.3. The issue arises in the default mode of the application, where it listens on all network interfaces. An unauthenticated remote shutdown can be triggered by sending a GET request to the /SHUTDOWN%20THE%20SERVER endpoint. This request causes the WordNet Browser HTTP server to terminate immediately, disrupting service availability.

Impact

Exploitation of this vulnerability leads to an immediate and uncontrolled shutdown of the WordNet Browser HTTP server, causing a denial-of-service condition. The server's process exits without a controlled shutdown, which can be disruptive to users.

Reproduction

To reproduce this vulnerability, start the NLTK WordNet Browser in Docker using the default settings, which include running the server on all interfaces. Once the server is running, send a GET request to the shutdown endpoint. The server will terminate immediately, confirming the denial-of-service condition.

Remediation

Users can update to NLTK version 3.9.4 or later, where this vulnerability has been patched.