CVE-2026-12243

A flaw was found in NLTK. An attacker can exploit a path traversal vulnerability by providing specially crafted input to nltk.data.load or nltk.data.find. This allows the attacker to read arbitrary files accessible to the Python process, leading to information disclosure. The vulnerability arises...

CVE-2026-12243 Path Traversal via Percent-Encoding in nltk.data.find() and nltk.data.load()

NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue 3504. The UNSAFENOPROTOCOLRE regex in nltk/data.py checks for literal ../ sequences but fails to account for percent-encoded traversal sequences such as ..%2f. The url2pathname function decodes...

CVE-2026-12243

NLTK 3.9.4 is documented to be vulnerable to a path traversal attack due to an incomplete fix (GitHub Issue #3504). The root cause is that the _UNSAFE_NO_PROTOCOL_RE regex in nltk/data.py only checks for literal ../ sequences and does not account for percent-encoded traversal such as ..%2f. Even ...

Arbitrary File Read via Percent-Encoded Path Traversal in nltk.data.find() / nltk.data.load() - Incomplete Fix of Issue #3504

The security fix for path traversal PR 3522, pathsec module that was merged into NLTK 3.9.3 to address GitHub Issue 3504 is incomplete. The UNSAFENOPROTOCOLRE regex in data.py:57 checks for literal ../ but url2pathname on line 653 decodes percent-encoded sequences after the validation, not before...