CVE-2026-126301

MEDIUM 5.3

NLTK from 3.6 before 3.10.4 Quadratic CPU Exhaustion via LegalitySyllableTokenizer.tokenize

CVSS Score

5.3

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-407
Vendor	nltk
Product	nltk
Published	Nov 13, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Affected Versions

nltk / nltk

3.6 < 3.10.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/nltk/nltk/security/advisories/GHSA-gpwc-27cw-rh9r vulncheck.com: https://www.vulncheck.com/advisories/nltk-from-3.6-before-3.10.4-quadratic-cpu-exhaustion-via-legalitysyllabletokenizer-tokenize

Credits

🔍 manus-pi 🔍 manus-use