NLTK: Corpus Reader Sandbox Bypass

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...

EUVD-2026-65524

NLTK: Corpus Reader Sandbox Bypass...

GHSA-3GQ4-3J92-5W49 NLTK: Corpus Reader Sandbox Bypass

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...

NLTK: Corpus readers follow symlinks outside trusted roots despite pathsec enforcement

Summary Several corpus readers still step outside NLTK's symlink-aware trusted-root model. They derive in-root paths from trusted corpus state, convert those paths back into plain strings, and reopen them with built-in open rather than nltk.pathsec.open. Details - Vulnerability type: Path travers...

GHSA-P4RW-RVV2-7XWR NLTK: Corpus readers follow symlinks outside trusted roots despite pathsec enforcement

Summary Several corpus readers still step outside NLTK's symlink-aware trusted-root model. They derive in-root paths from trusted corpus state, convert those paths back into plain strings, and reopen them with built-in open rather than nltk.pathsec.open. Details - Vulnerability type: Path travers...

EUVD-2026-65526

NLTK: Corpus readers follow symlinks outside trusted roots despite pathsec enforcement...

EUVD-2026-65440

NLTK: Allowlisted pickle loaders still permit code execution in current source...

NLTK: Allowlisted pickle loaders still permit code execution in current source

Summary The current source tree still allows arbitrary code execution during supposedly safer allowlisted pickle loading. The allowlist trusts whole module namespaces instead of exact safe globals, so crafted pickles can invoke dangerous in-namespace callables through pickle REDUCE. Details -...

GHSA-X99W-6FGC-PMFW NLTK: Allowlisted pickle loaders still permit code execution in current source

Summary The current source tree still allows arbitrary code execution during supposedly safer allowlisted pickle loading. The allowlist trusts whole module namespaces instead of exact safe globals, so crafted pickles can invoke dangerous in-namespace callables through pickle REDUCE. Details -...

NLTK: Entity-expansion DoS (billion laughs) via remaining raw ElementTree parses

Several XML parsing sites in NLTK still used xml.etree.ElementTree directly, which honours declarations in a document's internal DTD subset. A crafted document a few hundred bytes long can expand to megabytes in memory each nesting level multiplies by ten, a denial-of-service. Affected call sites...

EUVD-2026-65227

NLTK: Entity-expansion DoS billion laughs via remaining raw ElementTree parses...

GHSA-97QJ-X29F-37W7 NLTK: Entity-expansion DoS (billion laughs) via remaining raw ElementTree parses

Several XML parsing sites in NLTK still used xml.etree.ElementTree directly, which honours declarations in a document's internal DTD subset. A crafted document a few hundred bytes long can expand to megabytes in memory each nesting level multiplies by ten, a denial-of-service. Affected call sites...

NLTK: pathsec SSRF protection can be bypassed when a proxy is configured

Summary Current NLTK source reopens SSRF in proxied environments. pathsec.urlopen validates the requested hostname locally, but once proxy inheritance is enabled the real fetch is performed by the proxy rather than by the validated direct-connect socket path. Details - Vulnerability type:...

EUVD-2026-65228

NLTK: pathsec SSRF protection can be bypassed when a proxy is configured...

GHSA-6WW7-3FRV-CQXH NLTK: pathsec SSRF protection can be bypassed when a proxy is configured

Summary Current NLTK source reopens SSRF in proxied environments. pathsec.urlopen validates the requested hostname locally, but once proxy inheritance is enabled the real fetch is performed by the proxy rather than by the validated direct-connect socket path. Details - Vulnerability type:...

EUVD-2026-65229

NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution...

NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution

Summary The NLTK library's TransitionParser.parse method deserializes model files using pickleload with the default restricted=False parameter, allowing arbitrary Python code execution when loading a malicious model file. The library provides a RestrictedUnpickler class for safe deserialization,...

GHSA-RHP5-R9X4-F5G2 NLTK: Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution

Summary The NLTK library's TransitionParser.parse method deserializes model files using pickleload with the default restricted=False parameter, allowing arbitrary Python code execution when loading a malicious model file. The library provides a RestrictedUnpickler class for safe deserialization,...

EUVD-2026-64339

NLTK: Symlink-based arbitrary file read in IPIPANCorpusReader, bypasses nltk.pathsec entirely...

GHSA-3HHW-38PF-PXJ6 NLTK: Symlink-based arbitrary file read in IPIPANCorpusReader, bypasses nltk.pathsec entirely

Summary IPIPANCorpusReader nltk/corpus/reader/ipipan.py exposes public methods, channels, domains, categories, and fileidschannels=..., that accept a caller supplied fileids list and read a file via a completely unprotected builtin open call, with no nltk.pathsec involvement at all. A symlink...