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CVE-2026-80205— NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regex

Quick assessment

Affected
nltk nltk
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Natural Language Toolkit是Natural Language Toolkit组织开源的一个自然语言处理工具包。 Natural Language Toolkit 3.10.0之前版本存在资源管理错误漏洞，该漏洞源于Text.findall()和TokenSearcher.findall()方法接受用户提供的正则表达式而未验证或超时，容易受到正则表达式拒绝服务攻击，可能导致CPU饱和和拒绝服务。

CVSS 7.5 · High EPSS 0.65% · P51

Possible ATT&CK Techniques 1 AI

T1480 · Execution Guardrails

Affected Version Matrix 2

VendorProduct Version RangeStatus
nltk nltk < 3.10.0 affected
3.10.0 unaffected
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I. Basic Information for CVE-2026-80205

Vulnerability Information
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Vulnerability Title
NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regex
Source: CVE Program / CVE List V5
Vulnerability Description
NLTK versions before 3.10.0 contain a regular expression denial of service vulnerability in Text.findall() and TokenSearcher.findall() methods that accept user-supplied regular expressions without validation or timeout. Attackers can supply crafted regex patterns that cause catastrophic backtracking, resulting in indefinite CPU saturation and denial of service to all users of the Python process.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5
Vulnerability Title
Natural Language Toolkit 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Natural Language Toolkit是Natural Language Toolkit组织开源的一个自然语言处理工具包。 Natural Language Toolkit 3.10.0之前版本存在资源管理错误漏洞，该漏洞源于Text.findall()和TokenSearcher.findall()方法接受用户提供的正则表达式而未验证或超时，容易受到正则表达式拒绝服务攻击，可能导致CPU饱和和拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
nltk nltk 0 ~ 3.10.0 -

II. Public POCs for CVE-2026-80205

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III. Intelligence Information for CVE-2026-80205

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Other References for CVE-2026-80205 (2)

IV. Related Vulnerabilities

Same product: nltk
Same vendor: nltk
Same weakness: CWE-1333

V. Comments for CVE-2026-80205

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