AUGUST 16, 2026
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Case File

CVE-2026-12261

MEDIUM · CVSS 5.3 EPSS 0.19%

Source: NVD + CISA KEV + EPSS · Published 2026-08-07 · Last synced 2026-08-16

CyberRota Analysis

AI-Generated

The vulnerability in the NLTK downloader allows for cross-package resource and model poisoning due to improper handling of package archives, which are extracted into shared namespaces instead of isolated directories. This design flaw permits one package to overwrite another's trusted resources, potentially compromising machine learning pipelines and affecting reproducibility in sensitive environments. Developers and organizations utilizing NLTK for natural language processing tasks should prioritize addressing this issue to mitigate risks associated with resource integrity and security.

CVE
CVE-2026-12261
Severity
MEDIUM
CVSS
5.3
EPSS
0.19%

Original NVD 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.