Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-80205

CVE-2026-80205HIGH

NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regex

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   N   N   N   H    8.7   .0065   49.4     —

AFFECTED
  Product  Versions     Fixed
  nltk     unspecified  3.10.0

TIMELINE
  Aug 25  Reserved by VulnCheck
  Aug 26  Published (CNA: VulnCheck)
  Sep 1   EXPLOIT PUBLISHED — CVE-2026-80205 (nltk). Public exploit reference added.

CWE-1333 · CNA: VulnCheck · CVSS v4.0 · 3 references · NVD status: Modified

Description

NLTK versions before 3.10.0 contain a regular expression denial of service vulnerability in Text.findall() and TokenSearcher.findall() methods that accept user-supplied regular expressions without validation or timeout. Attackers can supply crafted regex patterns that cause catastrophic backtracking, resulting in indefinite CPU saturation and denial of service to all users of the Python process.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 25, 2026	Reserved	Reserved by VulnCheck
August 26, 2026	Published	Published (CNA: VulnCheck)
September 1, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-80205 (nltk). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
nltk	nltk	—	—	3.10.0

Weaknesses

CWE-1333

References (3)

http://www.openwall.com/lists/oss-security/2026/09/01/3
https://github.com/nltk/nltk/security/advisories/GHSA-rrv8-h7p8-rx55 [Exploit, Vendor Advisory]
https://www.vulncheck.com/advisories/nltk-before-3.10.0-redos-via-text-findall-unvalidated-regex [Third Party Advisory]

Authoritative record: CVE-2026-80205 at cve.org

Vendors: nltk

Weaknesses: CWE-1333

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-80205 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.