CVE-2026-126301

CVSS 6.9 (medium) · published 2026-11-13

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.

Weakness: CWE-407

Source: NVD CVE-2026-126301

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

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