CVE-2026-78683

Name of the Vulnerable Software and Affected Versions NLTK versions prior to 3.10.0

Description An unsafe pickle deserialization issue exists in the TransitionParser.parse() function. The function utilizes pickle load() with the restricted parameter set to False, which directs deserialization through WarningUnpickler. Because WarningUnpickler does not override the find class() method, it allows arbitrary class resolution. This enables an attacker to execute arbitrary Python code with the privileges of the application user by providing a specially crafted model file containing pickle gadget chains (sequences of objects that trigger unintended code execution during deserialization).

Recommendations Update NLTK to version 3.10.0 or later.