CVE-2021-3828

7.5 highEPSS 1.6%

High (7.5) in nltk nltk. EPSS 1.6% chance of exploitation in the next 30 days. Fixed in nltk 3.6.4.

nltk is vulnerable to Inefficient Regular Expression Complexity

Severity

7.5 high

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 1.6% chance of exploitation in the next 30 days; higher than 75% of CVEs (scores of 2026-10-31)
CWEs: CWE-697, CWE-1333
Published: 2021-09-27
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Advisory	Ecosystem	Package	Affected	Fixed in
GHSA-2ww3-fxvq-293j	PyPI	nltk	<3.6.4	3.6.4
PYSEC-2021-356	PyPI	nltk	<3.6.4	3.6.4