CVE-2025-14009 nltk CVE debrief

Who should care

This vulnerability should be of high concern to developers and users of the NLTK library, as it can lead to full system compromise, including file system access, network access, and potential persistence mechanisms. Organizations using NLTK in their applications or products should prioritize patching this vulnerability to prevent potential attacks.

Technical summary

The vulnerability is caused by the lack of path validation and security checks in the _unzip_iter function of nltk/downloader.py. This function uses zipfile.extractall() to extract downloaded packages without validation, allowing attackers to craft malicious zip packages that can execute arbitrary code when extracted. The vulnerability is particularly severe because NLTK assumes all downloaded packages are trusted, and malicious packages can contain Python files that are executed automatically upon import.

Defensive priority

High priority should be given to patching this vulnerability, as it can lead to remote code execution and full system compromise. Organizations should ensure that all instances of NLTK are updated to a patched version as soon as possible.

Recommended defensive actions

• Update NLTK to a patched version
• Implement additional security checks for downloaded packages
• Monitor for suspicious activity related to NLTK usage
• Restrict access to NLTK downloader functionality
• Perform regular vulnerability scans and updates

Evidence notes

The CVE-2025-14009 vulnerability was reported by security researchers and has been confirmed by the NVD. The vulnerability affects all versions of NLTK and has a CVSS score of 8.8, indicating a high severity. The vulnerability is caused by the lack of path validation and security checks in the _unzip_iter function of nltk/downloader.py.

Official resources