Directory Traversal Affecting py3-nltk package, versions <3.10.0-r0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-CHAINGUARDLATEST-PY3NLTK-17896649
- published9 Jul 2026
- disclosed30 Jun 2026
Introduced: 30 Jun 2026
CVE-2026-12243 (opens in a new tab)How to fix?
Upgrade Chainguard py3-nltk to version 3.10.0-r0 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream py3-nltk package and not the py3-nltk package as distributed by Chainguard.
See How to fix? for Chainguard relevant fixed versions and status.
NLTK version 3.9.4 is vulnerable to a path traversal attack due to an incomplete fix for GitHub Issue #3504. The _UNSAFE_NO_PROTOCOL_RE 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 these sequences after the validation step, allowing an attacker to bypass the protection. This vulnerability enables an attacker to read arbitrary files accessible to the Python process by controlling the resource name parameter passed to nltk.data.load() or nltk.data.find(). The issue affects applications that rely on NLTK for resource loading, including NLP web applications, Jupyter notebooks, and CLI tools. The default pathsec.ENFORCE=False setting exacerbates the impact by not blocking the file read at the open() stage.