NLTK · GHSA-jh6r-h4rx-2j3w · Package
NO FIX YET · SEE WHAT TO DO
NLTK before 3.10.4 has a CCG lexicon parser (fromstring) whose string handling runs in quadratic time on wide bracket bodies or operator chains. A remote attacker who supplies such lexicon text can exhaust CPU and block worker threads.
first public Nov 13, 2026 · 1 source
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Applications that parse CCG lexicon text with NLTK's fromstring, especially where the lexicon comes from users or untrusted sources. This advisory is withdrawn as a duplicate of GHSA-89p3-fcch-88ph, so check that advisory for the authoritative details. Teams that only use NLTK on trusted, local data can skip it.
Not affected if no-ccg-parser-use, trusted-input-only
Who cares nltk, python
pip show nltkfromstring on input that comes from outside the applicationnltk to 3.10.4 or laterThis advisory has been withdrawn because it is a duplicate of GHSA-89p3-fcch-88ph. This link is maintained to preserve external references.
NLTK before 3.10.4 contains a denial of service vulnerability in the CCG lexicon parser fromstring that allows remote attackers to exhaust CPU by supplying wide inputs. Attackers can submit lexicon text with long flat bracket bodies or operator chains, triggering quadratic string re-slicing in matchBrackets and augParseCategory that blocks worker threads.
This page as .md · .json · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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