CVE-2026-78683

A flaw was found in NLTK. This vulnerability allows arbitrary code execution due to unsafe deserialization, where data loaded from storage is converted back into active objects without adequate restrictions. When the TransitionParser component processes a model file, it fails to enforce safe...

NLTK AllowlistUnpickler dotted-name validation bypass allows remote code execution

NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft...

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,...

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-2026-65229

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

EUVD-2026-67076

NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots...

GHSA-8MGP-746C-J5XP NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots

Summary Several model-artifact APIs still treat caller-controlled model paths as ordinary filenames even when NLTK path security is enforced. The same outside-root paths are rejected by guarded helpers, but these public read and write flows still use raw file APIs. Details - Vulnerability type:...

NLTK: Model-artifact APIs bypass pathsec and touch files outside allowed roots

Summary Several model-artifact APIs still treat caller-controlled model paths as ordinary filenames even when NLTK path security is enforced. The same outside-root paths are rejected by guarded helpers, but these public read and write flows still use raw file APIs. Details - Vulnerability type:...

CVE-2026-71513

A flaw was found in NLTK. A remote attacker can achieve remote code execution by crafting untrusted transition-parser models. This vulnerability exists in the AllowlistUnpickler, which incorrectly validates only the pickle module string and not the global name. This allows attackers to bypass the...

CVE-2026-81726: External Control of File Name or Path

NLTK through 3.10.3 contains a path traversal vulnerability in model-artifact APIs that bypass pathsec enforcement by using raw file operations on caller-controlled paths. Attackers can read or write files outside allowed sandbox roots through TransitionParser, AveragedPerceptron, PerceptronTagge...

Deserialization of Untrusted Data

Overview nltk is a Natural Language Toolkit NLTK is a Python package for natural language processing. Affected versions of this package are vulnerable to Deserialization of Untrusted Data through the parse method in nltk/parse/transitionparser.py. An attacker can execute arbitrary Python code by...

Duplicate Advisory: [CWE-502] Unsafe Pickle Deserialization in TransitionParser Allows Remote Code Execution

Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-rhp5-r9x4-f5g2. This link is maintained to preserve external references. Original Description NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the...

PYSEC-2026-3734

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

PYSEC-2026-3734

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

CVE-2026-78683

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

DEBIAN-CVE-2026-78683

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

CVE-2026-78683 NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

CVE-2026-78683 NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

CVE-2026-78683

NLTK before 3.10.0 affected versions =3.9.4 contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse method nltk/parse/transitionparser.py. The method calls pickleload with the default restricted=False, routing deserialization through WarningUnpickler, which does not...

CVE-2026-78683

NLTK versions ≤3.9.4 contain an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with restricted=False, routing through WarningUnpickler , which does not override find_class() and thus permits arbit...