nltk up to 3.9.2 path traversal

Summaryinfo

A vulnerability was found in nltk up to 3.9.2 and classified as critical. Affected is the function WordListCorpusReader/TaggedCorpusReader/BracketParseCorpusReader. Such manipulation leads to path traversal. This vulnerability is uniquely identified as CVE-2026-0847. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in nltk up to 3.9.2. Affected by this issue is the function WordListCorpusReader/TaggedCorpusReader/BracketParseCorpusReader. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to 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. Impacted is confidentiality, integrity, and availability. CVE summarizes:

A vulnerability in NLTK versions up to and including 3.9.2 allows arbitrary file read via path traversal in multiple CorpusReader classes, including WordListCorpusReader, TaggedCorpusReader, and BracketParseCorpusReader. These classes fail to properly sanitize or validate file paths, enabling attackers to traverse directories and access sensitive files on the server. This issue is particularly critical in scenarios where user-controlled file inputs are processed, such as in machine learning APIs, chatbots, or NLP pipelines. Exploitation of this vulnerability can lead to unauthorized access to sensitive files, including system files, SSH private keys, and API tokens, and may potentially escalate to remote code execution when combined with other vulnerabilities.

The advisory is available at huntr.com. This vulnerability is handled as CVE-2026-0847 since 01/11/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for 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 03/07/2026). This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

The vulnerability scanner Nessus provides a plugin with the ID 301115 (Linux Distros Unpatched Vulnerability : CVE-2026-0847), which helps to determine the existence of the flaw in a target environment.

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

The vulnerability is also documented in the vulnerability database at Tenable (301115). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• nltk

Version

• 3.9.0
• 3.9.1
• 3.9.2

CPE 2.3info

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CPE 2.2info

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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