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Advisory record · GHSA-qvv7-cg9c-w4x3

Natural Language Toolkit (NLTK): DNS-rebinding SSRF filter bypass in nltk.pathsec.urlopen (nltk.download / nltk.data.load) defeats ENFORCE mode

CVSS 8.6 High

Published by the GitHub Advisory Database at 31 Jul 2026, 16:51 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-qvv7-cg9c-w4x3 · CVE-2026-12075 · PYSEC-2026-3583
Weakness (CWE)
CWE-918
Tags
Published
31 Jul 2026
Updated
10 Sept 2026

Machine-written summary

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

GHSA-qvv7-cg9c-w4x3 affects nltk versions before 3.10.0, where the nltk.pathsec SSRF filter can be bypassed with DNS rebinding. The filter checks the IP a hostname resolves to, but the actual connection resolves the hostname again, so an attacker controlling DNS can pass validation with a public address and connect to an internal or loopback address, even in ENFORCE mode. The attacker can then read full responses from internal services and cloud metadata endpoints. Upgrade nltk to 3.10.0 or later.

Written 4 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
8.6 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N GitHub Advisory Database
  • CISA KEV Not listed.
  • EPSS No score.

Timeline

  1. 31 Oct 2026, 14:29 UTC First seen by agentprime
  2. 31 Oct 2026, 14:29 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.