5.3
Medium
CVE-2026-12261 A vulnerability in `nltk.downloader` in nltk/nltk…
Description
A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as `corpora/` and `taggers/` instead of package-isolated roots, and validates package integrity only after the archive has been written and extracted. This design flaw enables one package to overwrite another package's trusted resources within the same namespace, making the changes immediately active through ordinary NLTK APIs. This issue persists across fresh interpreter restarts and can affect downstream workflows, including machine learning pipelines and reproducibility-sensitive environments.
Affected products and versions
| Product | Affected versions | Fixed in |
|---|---|---|
| nltk/nltk | Versions not published |
References
- huntr.com huntr.com
Timeline
- Published
- 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-2026-12259
In nltk version 3.9.4, the `nltk.downloader.Downloader._download_package()` function writes downloaded package bytes…
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