CVE-2026-62388: NLTK: Default ENFORCE=False Disables All pathsec Security Controls

NLTK’s pathsec.py security module defaults to ENFORCE=False (line 24), which means all 8 security validation functions only emit RuntimeWarning instead of raising exceptions when violations are detected.

The pathsec module was introduced as the fix for CVE-2024-39705 (arbitrary code execution via pickle) and CVE-2026-0846 (path traversal). However, with ENFORCE=False as the default:

1. pathsec.open(’/etc/passwd’) succeeds (reads the file, emits warning)
2. pathsec.validate_network_url(‘http://169.254.169.254/…’) succeeds (warning only)
3. pickle.loads() via nltk.data.load() proceeds despite unsafe source (warning only)

Every security gate follows the same pattern:

ENFORCE = os.environ.get('NLTK_PATHSEC_ENFORCE', '').lower() in ('1', 'true', 'yes')

def validate_something(path):
if is_violation(path):
if ENFORCE:
raise SecurityError('...')  # Only raised when env var is set
else:
warnings.warn('...', RuntimeWarning)  # Default: warning only