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Vulnerability record · CVE-2026-33236 · published 20 March 2026

CVE-2026-33236: Nltk path traversal 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, the NLTK downloader does not validate the `subdir` and `id` attributes when processing remote XML index files. Attackers can control a remote XML index server to provide malicious values containing path traversal sequences (such as `../`), which can lead to arbitrary directory creation, arbitrary file creation, and arbitrary file overwrite. Commit 89fe2ec2c6bae6e2e7a46dad65cc34231976ed8a patches the issue.

8.1 CVSS 3.1 High EPSS 0.71% · top 48.5% CWE-22 · Path traversal
8.1CVSS 3.1 base score
0.71%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
9References, 1 tagged exploit
21 Jul 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, the NLTK downloader does not validate the `subdir` and `id` attributes when processing remote XML index files. Attackers can control a remote XML index server to provide malicious values containing path traversal sequences (such as `../`), which can lead to arbitrary directory creation, arbitrary file creation, and arbitrary file overwrite. Commit 89fe2ec2c6bae6e2e7a46dad65cc34231976ed8a patches the issue.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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/89fe2ec2c6bae6e2e7a46dad65cc34231976ed8a Patch
https://github.com/nltk/nltk/security/advisories/GHSA-469j-vmhf-r6v7 ExploitVendor Advisory
https://access.redhat.com/errata/RHSA-2026:10184
https://access.redhat.com/errata/RHSA-2026:19712
https://access.redhat.com/errata/RHSA-2026:37275
https://access.redhat.com/errata/RHSA-2026:42644
https://access.redhat.com/security/cve/CVE-2026-33236
https://bugzilla.redhat.com/show_bug.cgi?id=2449824
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33236.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-2026-33236), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.