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TI-2021-02759 Aliases CVE-2021-3828GHSA-2ww3-fxvq-293j

Inefficient Regular Expression Complexity in nltk/nltk

Priority LOW 36CWE-1333Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-1333.

Summary

nltk is vulnerable to Inefficient Regular Expression Complexity

Why it matters now

EPSS 0.01592 75th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed nltk (PyPI): 3.6.4

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
nltknltk/nltkup to 3.6.3—No fix listedCNA
—nltk (PyPI)before 3.6.43.6.4Patch availableGHSA-2ww3-fxvq-293j
  • nltk/nltk Vendornltk Affected up to 3.6.3 Fixed in — No fix listed CNA
  • nltk (PyPI) Vendor— Affected before 3.6.4 Fixed in 3.6.4 Patch available GHSA-2ww3-fxvq-293j

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*up to 3.6.3Vulnerablenltk
  • cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:* Versions up to 3.6.3 Vulnerable ·nltk

Remediation

  • Fix · GHSA-2ww3-fxvq-293j nltk (PyPI) Fixed in 3.6.4 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-3828
  2. 2026-10-03 Alias added: GHSA-2ww3-fxvq-293j

References

Exploit 1

Patch 1

Advisory 2

Other 3

  • TI-2026-00629 Arbitrary Code Execution in NLTK StanfordSegmenter via Untrusted JAR Loading CVSS 3.0CRITICAL 10.0
  • TI-2025-12800 Zip Slip Vulnerability in nltk/nltk Leading to Remote Code Execution CVSS 3.0CRITICAL 10.0
  • TI-2026-55173 NLTK before 3.10.3 JVM Argument Injection via Per-Call Options CVSS 4.0CRITICAL 9.3
  • TI-2026-55155 NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization CVSS 4.0CRITICAL 9.3
  • TI-2026-56370 nltk PorterStemmer before 3.10.3 Quadratic-time DoS CVSS 4.0HIGH 8.7
  • TI-2026-55172 NLTK 3.10.2 Path Traversal via corpus-reader constructors CVSS 4.0HIGH 8.8
See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences