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CVE-2026-86428— commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes

Quick assessment

Affected
thephpleague commonmark
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.

The League of Extraordinary Packages league/commonmark是The League of Extraordinary Packages组织开源的一款Markdown解析组件。 The League of Extraordinary Packages league/commonmark 1.5.0至2.10.0之前版本存在资源管理错误漏洞，该漏洞源于AttributesExtension在处理不同名称的属性时，攻击者可通过提交含有大量不同属性名的Markdow

CVSS 7.5 · High EPSS 0.49% · P42

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 2

VendorProduct Version RangeStatus
thephpleague commonmark 1.5.0< 2.10.0 affected
2.10.0 unaffected
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I. Basic Information for CVE-2026-86428

Vulnerability Information
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Vulnerability Title
commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes
Source: CVE Program / CVE List V5
Vulnerability Description
commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing legitimate requests from completing.
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
算法复杂性
Source: CVE Program / CVE List V5
Vulnerability Title
The League of Extraordinary Packages league/commonmark 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
The League of Extraordinary Packages league/commonmark是The League of Extraordinary Packages组织开源的一款Markdown解析组件。 The League of Extraordinary Packages league/commonmark 1.5.0至2.10.0之前版本存在资源管理错误漏洞，该漏洞源于AttributesExtension在处理不同名称的属性时，攻击者可通过提交含有大量不同属性名的Markdow
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
thephpleague commonmark 1.5.0 ~ 2.10.0 -

II. Public POCs for CVE-2026-86428

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III. Intelligence Information for CVE-2026-86428

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Vendor Advisories for CVE-2026-86428 (2)

Same Patch Batch · thephpleague · 2026-09-07 · 8 CVEs total

CVE-2026-86430 7.5 HIGH league/commonmark before 2.9.1 Denial of Service via parsing
CVE-2026-86429 7.5 HIGH commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes
CVE-2026-86435 7.5 HIGH commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote
CVE-2026-86434 7.5 HIGH commonmark 2.0.0 through 2.8.3 Denial of Service via Slug Collision
CVE-2026-86433 7.5 HIGH commonmark 1.5.0 before 2.8.4 Denial of Service via Attributes
CVE-2026-86431 7.2 HIGH commonmark before 2.9.1 XSS via AttributesExtension form feed bypass
CVE-2026-86432 5.3 MEDIUM commonmark 2.0.0 before 2.8.4 Denial of Service via XML

IV. Related Vulnerabilities

Same product: commonmark
Same vendor: thephpleague
Same weakness: CWE-407

V. Comments for CVE-2026-86428

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