CVE-2026-81724

Summary

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.

Affected Software

Weaknesses

• CWE-674: Uncontrolled Recursion

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: poc
  • Automatable: yes
  • Technical Impact: partial

Additional References

• https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh

References

• https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh
• https://www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion

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