CVE-2026-126301

EUVD-2026-125220
NLTK from 3.6 before 3.10.4 contains an algorithmic complexity vulnerability in LegalitySyllableTokenizer.tokenize that allows remote attackers to exhaust CPU by supplying long all-vowel tokens. Attackers can submit a token such as a long run of vowels, causing the unguarded onset reversal loop to perform quadratic work and deny service to syllabification components.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
VulnCheckCNA
5.3 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Base Score
CVSS 3.x
EPSS Score
Percentile: 44.01%
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources (CNA/ADP records, vendor advisories, Enginsight analysis).
VendorProductVersionSource
nltknltk
3.6 ≤
𝑥
< 3.10.4
CNA
Common Weakness Enumeration
References
https://github.com/nltk/nltk/security/advisories/GHSA-gpwc-27cw-rh9r
https://www.vulncheck.com/advisories/nltk-from-3.6-before-3.10.4-quadratic-cpu-exhaustion-via-legalitysyllabletokenizer-tokenize