CVE-2026-126301
NLTK from 3.6 before 3.10.4 Quadratic CPU Exhaustion via LegalitySyllableTokenizer.tokenize
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.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| nltk nltk nltk
pypi |
≥ 3.6; < 3.10.4 (affected, custom) 3.10.4 (unaffected, semver) Other versions: unaffected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 6.9 medium |
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N | CNA: VulnCheck |
| 3.1 / 5.3 medium |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | CNA: VulnCheck |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/nltk/nltk/security/advisories/GHSA-gpwc-27cw-rh9rCNA: VulnCheck · vendor-advisory
- https://www.vulncheck.com/advisories/nltk-from-3.6-before-3.10.4-quadratic-cpu-exhaustion-via-legalitysyllabletokenizer-tokenizeCNA: VulnCheck · third-party-advisory
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