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CVE-2026-71488— league/commonmark: Quadratic-time denial of service when parsing crafted Markdown

Quick assessment

Affected
thephpleague commonmark
Exploitation
Public or AI PoC available; prioritize validation
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 0.6.0版本至2.9.0之前版本存在资源管理错误漏洞，该漏洞源于特制Markdown行导致解析器在转换时存在二次时间复杂性，多个解析路径反复重新扫描行的增长部分，且Autol

CVSS 7.5 · High EPSS 0.63% · P50

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
thephpleague commonmark >= 0.6.0, < 2.9.0 affected
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I. Basic Information for CVE-2026-71488

Vulnerability Information
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Vulnerability Title
league/commonmark: Quadratic-time denial of service when parsing crafted Markdown
Source: CVE Program / CVE List V5
Vulnerability Description
league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 0.6.0 until 2.9.0, specially crafted Markdown lines can cause the parser to have quadratic time complexity when converting, because several parsing paths repeatedly rescan growing portions of a line to translate between character positions and byte positions, and the Autolink extension can also copy and validate the remaining line at every URL-like prefix, allowing an attacker who can submit Markdown for conversion to consume disproportionate CPU time with a comparatively small request. This issue is fixed in 2.9.0.
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 0.6.0版本至2.9.0之前版本存在资源管理错误漏洞，该漏洞源于特制Markdown行导致解析器在转换时存在二次时间复杂性，多个解析路径反复重新扫描行的增长部分，且Autol
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 >= 0.6.0, < 2.9.0 -

II. Public POCs for CVE-2026-71488

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 10719 chars
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III. Intelligence Information for CVE-2026-71488

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Patches & Fixes for CVE-2026-71488 (2)

Vendor Advisories for CVE-2026-71488 (1)

Vendor Pages for CVE-2026-71488 (1)

IV. Related Vulnerabilities

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