CVE-2026-81724CWE-674

CVE-2026-81724

Medium · published August 27, 2026

CVSS v3.1
5.3
EPSS
0%
Percentile
38.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS v4.0
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
EPSS
0.00456 · 38.6th percentile
Weakness
CWE-674 · Uncontrolled Recursion
Published
2026-08-27T21:21Z
Affected products (1)
ProductVersionsFixed in
nltk/nltk< 3.10.33.10.3
References (3)
https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh · [email protected]https://www.vulncheck.com/advisories/nltk-before-3.10.3-denial-of-service-via-uncontrolled-recursion · [email protected]https://github.com/nltk/nltk/security/advisories/GHSA-cw6x-m8jw-qmrh · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 27 AUG 14:51Z
    NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion
    cvelistv5