CVE-2026-33231

Publication date 20 March 2026

Last updated 27 May 2026

Ubuntu priority

Cvss 3 Severity Score

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
nltk	26.04 LTS resolute	Fixed 3.9.2-1ubuntu0.1~esm2
	25.10 questing	Vulnerable
	24.04 LTS noble	Fixed 3.8.1-1ubuntu0.1~esm2
	22.04 LTS jammy	Fixed 3.7-1ubuntu0.1~esm2
	20.04 LTS focal	Fixed 3.4.5-2ubuntu0.1~esm4
	18.04 LTS bionic	Fixed 3.2.5-1ubuntu0.1+esm4
	16.04 LTS xenial	Ignored end of ESM support, was needs-triage
	14.04 LTS trusty	Fixed 2.0~b9-0ubuntu4.1~esm6

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Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
nltk	Upstream: bbaae83

Severity score breakdown

Parameter	Value
Base score	7.5 · High
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Related Ubuntu Security Notices (USN)

USN-8302-1
NLTK vulnerabilities
25 May 2026