CVE-2026-33236

NLTK has a Downloader Path Traversal Vulnerability (AFO) - Arbitrary File Overwrite

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.

Affected

nltk

CVSS v3.1 CNA

8.1 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

EPSS

0.73% chance of exploitation in the next 30 days, 54th percentile

Published

2026-03-20

Updated

2026-07-21

Proof-of-concept exploits (1)

• advisories/GHSA-469j-vmhf-r6v7

Security advisories

• nltk/nltk/security/advisories/GHSA-469j-vmhf-r6v7
• nltk/nltk/commit/89fe2ec2c6bae6e2e7a46dad65cc34231976ed8a

References

• CVE Record
• NVD entry