Server-Side Request Forgery (SSRF) Affecting nltk package, versions <3.10.0-1


Severity

Recommended
0.0
medium
0
10

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Threat Intelligence

EPSS
0.24% (16th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-NLTK-19233198
  • published23 Aug 2026
  • disclosed22 Aug 2026

Introduced: 22 Aug 2026

NewCVE-2026-63311  (opens in a new tab)
CWE-918  (opens in a new tab)

How to fix?

Upgrade Debian:unstable nltk to version 3.10.0-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream nltk package and not the nltk package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

NLTK before 3.10.0 (affected versions <= 3.9.4) contains a server-side request forgery (SSRF) vulnerability in the validate_network_url() function in nltk/pathsec.py. The _resolve_hostname() helper catches OSError and ValueError during socket.getaddrinfo() and returns an empty list; when DNS resolution fails, the validation loop executes no IP checks and the function fails open, allowing urlopen() to proceed without validation. An attacker who can trigger DNS resolution failures or use DNS rebinding can bypass SSRF protections and reach restricted network resources, including cloud metadata endpoints (e.g., 169.254.169.254).

CVSS Base Scores

version 3.1