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CVE-2026-86433— commonmark 1.5.0 before 2.8.4 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.

CommonMark 1.5.0 至 2.8.4 之前的版本存在一个拒绝服务（DoS）漏洞，位于其“Attributes”扩展中。具体而言， 函数在对兄弟节点列表进行查找时采用了二次时间复杂度的扫描方式，导致性能低下。 未经身份验证的攻击者只需提交大约 32 KB 的重复属性块，就能使解析过程耗时超过 5 秒，从而耗尽服务器资源，引发拒绝服务问题。

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-2026-86433

Vulnerability Information
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Vulnerability Title
commonmark 1.5.0 before 2.8.4 Denial of Service via Attributes
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 Attributes extension where AttributesListener::findTargetAndDirection() performs quadratic-time sibling list scanning. Unauthenticated attackers can submit approximately 32 KB of repeated attribute blocks to cause parsing to take over 5 seconds, exhausting 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-2026-86433

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III. Intelligence Information for CVE-2026-86433

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Vendor Advisories for CVE-2026-86433 (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-2026-86428 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-2026-86433

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