NLTK Symlink Sandbox Bypass in FramenetCorpusReader

Executive Summary

CVE-2026-62384 is a symlink-based sandbox bypass in NLTK's FramenetCorpusReader. Attackers can place symlinks inside the corpus directory that bypass path validation checks. When methods like frame_by_name() or doc() are called with these symlink names, they resolve to files outside the intended directory, allowing unauthorized file access.

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Detection Guidance

Check NLTK version with pip show nltk. If version is before 3.10.2, the system is vulnerable. Inspect FramenetCorpusReader usage in code for methods like frame_by_name(), _lu_file(), or doc(). Look for symlinks in corpus directories that could bypass path checks.

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Impact Analysis

This vulnerability allows remote attackers to read arbitrary XML files outside the corpus root without privileges or user interaction. If you use NLTK versions before 3.10.2, an attacker could access sensitive files on your system by exploiting this flaw through normal API calls.

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Mitigation Strategies

Upgrade NLTK to version 3.10.2 or later immediately. Review and update any code using FramenetCorpusReader to use CorpusReader.open() or validate_path() with required_root. Remove or restrict write access to corpus directories to prevent symlink creation.

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