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CVE-2026-86435— commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote

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.

CommonMark 从 1.5.0 到 2.8.4 之前的版本中，Footnote（脚注）扩展存在一个拒绝服务（DoS）漏洞：脚注定义的重复检查缺失。攻击者可以通过构造包含重复脚注定义和引用的文档，引发二次方（quadratic）输出膨胀，从而消耗过多的内存和 CPU，耗尽服务器资源。

CVSS 7.5 · High

Affected Version Matrix 2

VendorProduct Version RangeStatus
thephpleague commonmark 1.5.0< 2.8.4 affected
2.8.4 unaffected
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I. Basic Information for CVE-2026-86435

Vulnerability Information
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Vulnerability Title
commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote
Source: CVE Program / CVE List V5
Vulnerability Description
commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Footnote extension that fails to deduplicate footnote definitions. Attackers can craft documents with duplicate footnote definitions and references to create quadratic output expansion, consuming excessive memory and CPU to exhaust server resources.
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

Affected Products

Vendor Product Affected Versions CPE Subscribe
thephpleague commonmark 1.5.0 ~ 2.8.4 -

II. Public POCs for CVE-2026-86435

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III. Intelligence Information for CVE-2026-86435

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Vendor Advisories for CVE-2026-86435 (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-2026-86434 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-2026-86428 7.5 HIGH commonmark 1.5.0 before 2.10.0 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-2026-86435

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