CVE-2026-12259

Fixed upstream EPSS <1%CVSS 5.3

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.

Published 2026-08-03 · CVE record · OSV

Products: nltk/nltk

Fixed upstream

Distro releases