Server-side Request Forgery (SSRF) Affecting nltk package, versions [,3.10.0)
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.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applicationsSnyk Learn
Learn about Server-side Request Forgery (SSRF) vulnerabilities in an interactive lesson.
Start learning- Snyk IDSNYK-PYTHON-NLTK-19233303
- published23 Aug 2026
- disclosed22 Aug 2026
- creditUnknown
Introduced: 22 Aug 2026
NewCVE-2026-63311 (opens in a new tab)How to fix?
Upgrade nltk to version 3.10.0 or higher.
Overview
nltk is a Natural Language Toolkit (NLTK) is a Python package for natural language processing.
Affected versions of this package are vulnerable to Server-side Request Forgery (SSRF) via the validate_network_url() DNS resolution path in nltk/pathsec.py. An attacker can make urlopen() reach restricted internal URLs by causing hostname resolution to fail, which leaves the validation loop with no resolved addresses to check and lets the request proceed without rejecting the target. When DNS is unavailable or returns an error for an attacker-supplied hostname, the SSRF filter fails open instead of blocking the request. This can expose internal services such as cloud metadata endpoints to network requests initiated by NLTK and bypass URL validation in applications that rely on it.