NLTK up to 3.10.2 CrubadanCorpusReader _load_lang_ngrams crubadan_code path traversal

Summaryinfo

A vulnerability was found in NLTK up to 3.10.2. It has been declared as problematic. This affects the function _load_lang_ngrams of the component CrubadanCorpusReader. Executing a manipulation of the argument crubadan_code can lead to path traversal. This vulnerability is registered as CVE-2026-71514. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability has been found in NLTK up to 3.10.2 and classified as problematic. This vulnerability affects the function _load_lang_ngrams of the component CrubadanCorpusReader. The manipulation of the argument crubadan_code 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. CVE summarizes:

NLTK 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader. _load_lang_ngrams joins the corpus root with crubadan_code, the column-0 value read from the corpus table.txt mapping file, and opens the result with the builtin open() rather than the pathsec-validated opener, so os.path.join discards the root when that value is absolute and the read escapes the corpus directory without the containment check nltk.pathsec applies when ENFORCE is set. An attacker who controls a corpus package can disclose file contents outside the corpus root through lang_freq, limited to paths ending in -3grams.txt whose contents parse as token count lines.

The advisory is available at github.com. This vulnerability was named CVE-2026-71514 since 08/06/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

Upgrading to version 3.10.3 eliminates this vulnerability.

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Productinfo

Name

• NLTK

Version

• 3.10.0
• 3.10.1
• 3.10.2

Website

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

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