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-2026-81722

CVE-2026-81722HIGH

nltk PorterStemmer before 3.10.3 Quadratic-time DoS

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   N   N   N   H    8.7   .0052   42.2     —

AFFECTED
  Product  Versions     Fixed
  nltk     unspecified  3.10.3

TIMELINE
  Aug 27  Reserved by VulnCheck
  Aug 27  Published (CNA: VulnCheck)
  Aug 31  EXPLOIT PUBLISHED — CVE-2026-81722 (nltk). Public exploit reference added.

CWE-407 · CNA: VulnCheck · CVSS v4.0 · 2 references · NVD status: Analyzed

Description

nltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). The _is_consonant() helper walks backward over the entire run of trailing 'y' characters on every call, and _measure() invokes it for each stem position, causing O(n^2) behavior. A single ~20-50 KB untrusted token consisting of a long run of the letter 'y' followed by a matching suffix (e.g., 'ness') can pin a CPU core for seconds to minutes, causing availability impact.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 27, 2026	Reserved	Reserved by VulnCheck
August 27, 2026	Published	Published (CNA: VulnCheck)
August 31, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-81722 (nltk). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
nltk	nltk	—	—	3.10.3

Weaknesses

CWE-407

References (2)

https://github.com/nltk/nltk/security/advisories/GHSA-ww6m-cw3f-q94g [Exploit, Vendor Advisory]
https://www.vulncheck.com/advisories/nltk-porterstemmer-before-3.10.3-quadratic-time-dos [Third Party Advisory]

Authoritative record: CVE-2026-81722 at cve.org

Vendors: nltk

Weaknesses: CWE-407

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-81722 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.