What’s Vulnerable › Vulnerabilities

CVE-2026-109956: NLTK through 3.10.3 Path Traversal via WekaClassifier Model Path

• Severity: high (CVSS 7.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-13 · updated 2026-10-26
• Weakness: CWE-22

Description

NLTK through 3.10.3 contains a path traversal vulnerability in WekaClassifier that allows attackers to bypass nltk.pathsec containment by supplying unvalidated model paths. Attackers controlling the model_filename or model argument can make the weka JVM write files via -d or probe files via -l outside allowed data roots.

Affected products

• Pypi Nltk: before 3.10.4; 0.8, 0.9, 0.9.3, 0.9.4, 0.9.5, 0.9.6 (+63) — fixed in 3.10.4
• nltk: through 3.10.3

How to fix

Upgrade to a fixed version: Pypi Nltk 3.10.4. Check the vendor advisory for mitigations.

References

• https://github.com/nltk/nltk/security/advisories/GHSA-j456-xh4h-cpf2
• https://www.vulncheck.com/advisories/nltk-through-3.10.3-path-traversal-via-wekaclassifier-model-path
• https://github.com/nltk/nltk/security/advisories/GHSA-j456-xh4h-cpf2

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