# CVE-2026-81724

## Summary

- **CVE ID:** CVE-2026-81724
- **Severity:** MEDIUM
- **CVSS Score:** 6.9 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N)
- **CWE:** CWE-674
- **Published:** Aug 27, 2026
- **Last Modified:** Aug 27, 2026

## Description

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 Products

- nltk — nltk (0)
- nltk — nltk (3.10.3)

## References

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

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.27%
- **EPSS Percentile:** 18.7

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._