CVE-2026-81724
NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.
- Published Aug 27, 2026
- CVSS 6.9 medium
- 0.5% chance of exploitation in the next 30 days (EPSS)
- Public exploit code is available
- A fix is available