Pypi · Nltk · CVE-2026-81724
**Name of the Vulnerable Software and Affected Versions**
NLTK versions prior to 3.10.3
**Description**
An uncontrolled recursion issue exists in the `nltk.featstruct.FeatStructReader` class. Unauthenticated attackers can trigger a denial of service by providing deeply nested feature-structure input, such as payloads with nested brackets. This exceeds Python's recursion limit and triggers an unhandled `RecursionError`, which crashes applications that parse user-supplied feature structures or feature grammars.
**Recommendations**
Update to version 3.10.3 or later.