NLTK: SSRF Fail-Open in validate_network_url() via DNS Resolution Failure — GHSA-3GQM-FCW5-W839

Summary

There is an SSRF vulnerability in NLTK 3.9.4's network URL validation. The validate_network_url() function in nltk/pathsec.py fails open when DNS resolution returns an error. The _resolve_hostname() helper at lines 193-234 catches OSError and ValueError during socket.getaddrinfo() and returns an empty list []. When this happens, the validation loop in validate_network_url() iterates over nothing (for addr in…

Timeline

Published by source

2026-09-02

Risk context

• Reported severity or threat level: medium.
• Reported CVSS score: 6.9 out of 10.
• Reported EPSS value: 0.00241.
• Review exposure for the affected product or family: pip: nltk.

Product

pip: nltk

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-3GQM-FCW5-W839

Source

GitHub

Vendor

GitHub

Published by source

2026-09-02

Last source activity

2026-09-02

Additional identifiers

CVE-2026-63311

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.