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  4. CVE 2026 126301 nltk from 36 before 3104 quadratic cpu exhaustion
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Back to active CVEs
Medium · CVSS 6.9CVE-2026-126301

NLTK from 3.6 before 3.10.4 Quadratic CPU Exhaustion via LegalitySyllableTokenizer.tokenizeCVE-2026-126301

Answer in brief

CVE-2026-126301 records a Medium severity (CVSS 6.9) vulnerability in NLTK from 3.6 before 3.10.4 Quadratic CPU Exhaustion via LegalitySyllableTokenizer.tokenize. The current sources do not mark it as known exploited. The current feed maps nltk/nltk (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Nov 13, 2026Updated Nov 13, 2026Source checked Nov 13, 2026First seen by HOL Nov 13, 2026Material review Nov 13, 2026
Upstream Advisory

Key facts

Risk
Medium · CVSS 6.9
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 6.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps nltk/nltk (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
nltk/nltkgeneric>=3.6 <3.10.43.10.4

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for nltk/nltk.
  2. 2Review the reported fix. Update nltk/nltk to 3.10.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Nov 13, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Nov 13, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Nov 13, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • Source referencevulncheck.com
Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Secret Exfiltration
EPSS
Not reported
CWE IDs
CWE-407
Source
CVE List V5
Source checked
Nov 13, 2026
References
2 linked sources
Open source record