CVE-2026-12259
In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes to disk and may extract
CVSS
5.3
Medium
EPSS
—
KEV
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Exploit Today
0
0-100
Published: Aug 3, 2026 · Last modified: Aug 3, 2026 · CWE-494
Not enough EPSS history yet.
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.