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THREAT OPS › Threat News › [GHSA] GHSA-cw6x-m8jw-qmrh (medium) — NLTK: Uncontrolled recursion in nltk.featstruct.FeatStructReader causes unhandled RecursionError (DoS) via deeply nested feature-structure input

[GHSA] GHSA-cw6x-m8jw-qmrh (medium) — NLTK: Uncontrolled recursion in nltk.featstruct.FeatStructReader causes unhandled RecursionError (DoS) via deeply nested feature-structure input

medgithub_advisoriesPublished 2026-09-02

GHSA-cw6x-m8jw-qmrh Severity: medium CVE: CVE-2026-81724

NLTK: Uncontrolled recursion in nltk.featstruct.FeatStructReader causes unhandled RecursionError (DoS) via deeply nested feature-structure input

### Summary

`nltk.featstruct.FeatStructReader` (used by `FeatStruct(str)` and by `FeatureGrammar.fromstring()`) parses feature-structure strings such as `[a=1]` with a recursive-descent parser th

Indicators of compromise

CVE-2026-81724cve

Original source: https://github.com/advisories/GHSA-cw6x-m8jw-qmrh