Duplicate Advisory: NLTK: Missing Post-Download Integrity Verification Allows Malicious Package Injection

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-5wp5-5229-5g6q. This link is maintained to preserve external references.

Original Description

In nltk version 3.9.4, the nltk.downloader.Downloader._download_package() function writes downloaded package bytes to disk and may extract them before enforcing SHA-256 or MD5 checksum validation. This allows an attacker to tamper with the package response body for info.url through a compromised mirror, malicious proxy, or other source-substitution condition, leading to the installation of attacker-controlled package bytes. The vulnerability can result in malicious corpus or model content being trusted by downstream users or applications.