NLTK: Quadratic CPU Exhaustion in `XMLCorpusView._read_xml_fragment()` — GHSA-VP2X-QP44-57V7

Summary

## Summary `XMLCorpusView._read_xml_fragment()` reads a corpus file in 1 KiB blocks, appending each block to a growing `fragment` string, then calls `_VALID_XML_RE.match(fragment)` on the full accumulated buffer every iteration. Because each iteration rescans the entire accumulated fragment, the total amount of work grows quadratically with input size. Commit `c9c332284` (CWE-1333) made each `match()` call linear.…

Timeline

Published by source

2026-09-02

Risk context

• Reported severity or threat level: medium.
• Reported CVSS score: 6.3 out of 10.
• Reported EPSS value: 0.00222.
• 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-VP2X-QP44-57V7

Source

GitHub

Vendor

GitHub

Published by source

2026-09-02

Last source activity

2026-09-02

Additional identifiers

CVE-2026-81723

Curated by

hlukh.ch

Related advisories and connections

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