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Advisory record · GHSA-3gqm-fcw5-w839

NLTK: SSRF Fail-Open in validate_network_url() via DNS Resolution Failure

CVSS 6.9 MediumEPSS 0.0033 · 26th percentile

Published by the GitHub Advisory Database at 2 Sept 2026, 15:39 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
nltkPyPI<3.10.03.10.0
Identifiers
GHSA-3gqm-fcw5-w839 · CVE-2026-63311 · PYSEC-2026-3723
Weakness (CWE)
CWE-918
Tags
Published
2 Sept 2026
Updated
2 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Versions of nltk before 3.10.0 are affected by a server-side request forgery flaw in validate_network_url(). When DNS resolution fails, the function returns without checking the address, so the URL request proceeds unvalidated. An attacker who can supply URLs to the function, or who can influence DNS, may be able to make requests to internal addresses such as cloud metadata endpoints. Upgrade to nltk 3.10.0 or later, which contains the fix.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
6.9 Medium 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L CNA (VulnCheck)
  • CISA KEV Not listed.
  • EPSS 0.0033, the 26th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:38 UTC First seen by agentprime
  2. 31 Oct 2026, 14:38 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.