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-2026-81725

CVE-2026-81725MEDIUM

NLTK before 3.10.3 Regular Expression Denial of Service via Pl196xCorpusReader

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   H   P   N   N   N   N   L    6.3   .0037   28.5     —

AFFECTED
  Product  Versions     Fixed
  nltk     unspecified  3.10.3

TIMELINE
  Aug 27  Reserved by VulnCheck
  Aug 27  Published (CNA: VulnCheck)
  Sep 1   EXPLOIT PUBLISHED — CVE-2026-81725 (nltk). Public exploit reference added.

CWE-400 · CNA: VulnCheck · CVSS v4.0 · 2 references · NVD status: Analyzed

Description

NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 27, 2026	Reserved	Reserved by VulnCheck
August 27, 2026	Published	Published (CNA: VulnCheck)
September 1, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-81725 (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-400

References (2)

https://github.com/nltk/nltk/security/advisories/GHSA-8mpw-7fpc-4gqj [Exploit, Vendor Advisory]
https://www.vulncheck.com/advisories/nltk-before-3.10.3-regular-expression-denial-of-service-via-pl196xcorpusreader [Third Party Advisory]

Authoritative record: CVE-2026-81725 at cve.org

Vendors: nltk

Weaknesses: CWE-400

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-81725 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.