CVE-2026-79674

## Summary NLTK corpus-reader constructors can still reach outside-root file and database reads before the `nltk.pathsec` sandbox boundary is enforced. The PoC shows the safe path blocked by `pathsec.open`, then `LinThesaurusCorpusReader` and `PanLexLiteCorpusReader` succeeding in the same process. ## Affected Product - Product: NLTK - Asset / component: `nltk.corpus.reader` constructors - Version tested: `3.10.2` - Deployment / package / tag: commit `474af1f5a94b1b8d53fc2b6defec3a2ce7633b74` / PyPI `nltk` - Environment used for verification: Python 3.13.14 ## Vulnerability Details - Vulnerability class: path sandbox bypass / external control of file path - Required privileges: none beyond the ability to supply a corpus root path to a consumer call site - Entry point: `LinThesaurusCorpusReader(root)` and `PanLexLiteCorpusReader(root)` - Trust boundary crossed: NLTK data-root sandbox enforced by `nltk.pathsec` - Root affected functions: - [CorpusReader.__init__](https://github.com/nltk/nltk/blob/474af1f5a94b1b8d53fc2b6defec3a2ce7633b74/nltk/corpus/reader/api.py#L73-L80) - [LinThesaurusCorpusReader.__init__](https://github.com/nltk/nltk/blob/474af1f5a94b1b8d53fc2b6defec3a2ce7633b74/nltk/corpus/reader/lin.py#L37-L43) - [PanLexLiteCorpusReader.__init__](https://github.com/nltk/nltk/blob/474af1f5a94b1b8d53fc2b6defec3a2ce7633b74/nltk/corpus/reader/panlex_lite.py#L45-L46) - Measured unsafe effect: outside-root file/database reads still happen with `ENFORCE=True` ## Root Cause `CorpusReader.__init__()` turns a string root into a `FileSystemPathPointer` without any `pathsec` validation, and these readers then use builtin `open()` or `sqlite3.connect()` directly on derived paths. The constructor path therefore never hits the sandbox guard that `pathsec.open()` enforces. ```python if zipfile: root = ZipFilePathPointer(zipfile, zipentry) else: root = FileSystemPathPointer(root) with open(path) as lin_file: ... self._c = sqlite3.connect(os.path.join(