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Vulnerability record · CVE-2026-33231 · published 20 March 2026

CVE-2026-33231: Nltk missing authentication for critical function vulnerability

Nltk · Nltk

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.

7.5 CVSS 3.1 High EPSS 1.5% · top 27.5% CWE-306 · Missing authentication for critical function
7.5CVSS 3.1 base score
1.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
9References, 1 tagged exploit
9 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/nltk/nltk/commit/bbaae83db86a0f49e00f5b0db44a7254c268de9b Patch
https://github.com/nltk/nltk/security/advisories/GHSA-jm6w-m3j8-898g ExploitVendor Advisory
https://access.redhat.com/errata/RHSA-2026:19712
https://access.redhat.com/errata/RHSA-2026:24977
https://access.redhat.com/errata/RHSA-2026:37275
https://access.redhat.com/errata/RHSA-2026:65126
https://access.redhat.com/security/cve/CVE-2026-33231
https://bugzilla.redhat.com/show_bug.cgi?id=2449836
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33231.json

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2026-0848Nltk improper input validation vulnerabilityNLTK versions <=3.9.2 are vulnerable to arbitrary code execution due to improper input validation in the StanfordSegmenter module. The module dynamic…EPSS 0.81%9.4CVE-2026-78683Nltk deserialization of untrusted data vulnerabilityNLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/p…EPSS 0.51%9.3CVE-2026-79675Nltk argument injection vulnerabilityNLTK before 3.10.3 fails to validate JVM options passed through the per-call options parameter in the java() function, allowing attackers to inject d…EPSS 0.78%9.3CVE-2026-79657Nltk deserialization of untrusted data vulnerabilityNLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead o…EPSS 1.3%8.8CVE-2026-79674Nltk vulnerabilityNLTK versions before 3.10.3 contain a path sandbox bypass vulnerability in corpus-reader constructors that allows attackers to read files outside the…EPSS 0.39%8.8CVE-2025-14009Nltk code injection vulnerabilityA critical vulnerability exists in the NLTK downloader component of nltk/nltk, affecting all versions. The _unzip_iter function in nltk/downloader.py…EPSS 0.95%8.7CVE-2026-81722Nltk vulnerabilitynltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). …EPSS 0.52%8.7CVE-2026-80205Nltk inefficient regular expression (redos) vulnerabilityNLTK versions before 3.10.0 contain a regular expression denial of service vulnerability in Text.findall() and TokenSearcher.findall() methods that a…EPSS 0.65%

Source: NIST National Vulnerability Database (record CVE-2026-33231), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.