NLTK from 3.2.5 before 3.10.4 contains an algorithmic complexity vulnerability in TreebankWordTokenizer.span_tokenize that allows remote attackers to cause quadratic CPU consumption through repeated list.pop(0) calls. Attackers can submit long runs of double-quote characters to services span-tokenizing untrusted text, exhausting a CPU core and degrading availability.
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Fixes

Solution

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Workaround

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History

Fri, 13 Nov 2026 09:45:00 +0000

Type Values Removed Values Added
Description NLTK from 3.2.5 before 3.10.4 contains an algorithmic complexity vulnerability in TreebankWordTokenizer.span_tokenize that allows remote attackers to cause quadratic CPU consumption through repeated list.pop(0) calls. Attackers can submit long runs of double-quote characters to services span-tokenizing untrusted text, exhausting a CPU core and degrading availability.
Title NLTK from 3.2.5 before 3.10.4 CPU Exhaustion via TreebankWordTokenizer.span_tokenize
First Time appeared Nltk
Nltk nltk
Weaknesses CWE-407
CPEs cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*
Vendors & Products Nltk
Nltk nltk
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

cvssV4_0

{'score': 6.9, 'vector': '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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-11-13T09:36:25.918Z

Reserved: 2026-11-10T20:15:54.612Z

Link: CVE-2026-126300

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-11-13T10:17:34.917

Modified: 2026-11-13T10:17:35.043

Link: CVE-2026-126300

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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Weaknesses