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    CVE-2026-86428

    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.

    Published:Sep 7, 2026
    Last Modified:Sep 8, 2026
    EPS:Sep 7, 2026
    EPSS Score:0.00279
    CVSS Score:7.5

    Affected Products

    Vendor
    Thephpleague
    Product
    Commonmark

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

    Related CVEs

    CVE-2024-58382 (CVSS 8.7) — league/commonmark versions before 2.6.0 contain polynomial time complexity vulnerabilities in Markdown parsing…
    CVE-2026-86435 (CVSS 8.7) — commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Footnote extensio…
    CVE-2026-86434 (CVSS 8.7) — league/commonmark versions >= 2.0.0 and < 2.8.4 (patched in 2.9.0) contain a denial of service vulnerability i…
    CVE-2026-86433 (CVSS 8.7) — commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Attributes extens…
    CVE-2026-86432 (CVSS 6.9) — commonmark versions from 2.0.0 before 2.8.4 contain a denial of service vulnerability in XmlRenderer that emit…
    CVE-2026-86431 (CVSS 6.9) — league/commonmark (thephpleague/commonmark) versions >= 2.7.0 and < 2.9.1 contain a cross-site scripting vulne…
    CVE-2026-86430 (CVSS 8.7) — league/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code bloc…
    CVE-2026-86429 (CVSS 8.7) — The league/commonmark (thephpleague/commonmark) library in versions >= 1.5.0 and < 2.9.1 contains quadratic pa…
    CVE-2026-71488 (CVSS 7.5) — league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 0.6.0 until 2.9.0, spec…
    CVE-2026-71478 (CVSS 6.1) — league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the …

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2026-86428 — Thephpleague (High 8.7) | CVE-DB