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5.3 Medium

CVE-2026-12259 In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes…

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.

Affected products and versions

Product Affected versions Fixed in
nltk/nltk Versions not published

References

Timeline

  1. Published
  2. Last modified

Other CVEs of nltk/nltk

The 12 CVEs of nltk/nltk →
CVE-2026-12372 A Server-Side Request Forgery (SSRF) vulnerability exists in nltk/nltk versions 3.9.4 and the current develop branch 3.7 Low CVE-2026-12261 A vulnerability in `nltk.downloader` in nltk/nltk… 5.3 Medium CVE-2026-12252 In nltk/nltk versions 3.9.3 and earlier, five Stanford interface classes (StanfordPOSTagger, StanfordNERTagger,… 7.8 High CVE-2026-12243 NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504 7.5 High
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