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 them before…

PriorityP429medium5.3CVSS 3.0

AVNACHPRNUIRSUCNIHAN

EPSS

0.10%

1.0th percentile

no history available

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.

Affected

1 ranges

Vendor	Product	Version range	Fixed in
nltk	nltk_nltk	unspecified – latest	—

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