NLTK contains a file sandbox bypass vulnerability in several model-artifact APIs that improperly handle caller-controlled model paths. Despite path security enforcement via pathsec, these APIs use raw file operations allowing reading and writing files outside the allowed sandbox roots. This affects model import and export functions such as TransitionParser.train, TransitionParser.parse, and AveragedPerceptron.save/load. The issue is confirmed in versions 3.9.4 and 3.10.0-rc2, with a fix available in version 1.0.8_25. Exploiting this flaw can lead to unauthorized file access and modification outside intended directories.