NLTK up to 3.10.3 WekaClassifier model_filename/model path traversal

Summaryinfo

A vulnerability categorized as critical has been discovered in NLTK up to 3.10.3. Affected by this vulnerability is an unknown functionality of the component WekaClassifier. Executing a manipulation of the argument model_filename/model can lead to path traversal. This vulnerability is registered as CVE-2026-109956. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in NLTK up to 3.10.3. It has been declared as critical. This vulnerability affects an unknown functionality of the component WekaClassifier. The manipulation of the argument model_filename/model with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-22. The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2026-109956 since 10/13/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/13/2026). This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

• NLTK

Version

• 3.10.0
• 3.10.1
• 3.10.2
• 3.10.3

Website

• Product: https://github.com/nltk/nltk/

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