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    CVE-2026-59928

    Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

    Published:Jul 8, 2026
    Last Modified:Jul 10, 2026
    EPS:Jul 8, 2026
    EPSS Score:0.00346
    CVSS Score:7.5

    Affected Products

    Vendor
    Lepture
    Product
    Mistune

    Exploits

    https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92qhttps://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-492 Regular Expression Exponential Blowup

    Related CVEs

    CVE-2026-76098 (CVSS 7.5) — Mistune is a Python Markdown parser with renderers and plugins. Versions 3.3.0 through 3.3.2 are vulnerable to…
    CVE-2026-59927 (CVSS 5.3) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the Include directive in src/m…
    CVE-2026-59924 (CVSS 5.9) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Include.parse() joins and norm…
    CVE-2026-59929 (CVSS 6.1) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the safe_url filter in src/mis…
    CVE-2026-59925 (CVSS 7.5) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed …
    CVE-2026-59926 (CVSS 5.3) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mis…
    CVE-2026-59923 (CVSS 6.1) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safe_url() does n…
    CVE-2026-59930 (CVSS 4.3) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfCont…
    CVE-2026-59922 (CVSS 7.5) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-…
    CVE-2026-49851 (CVSS 8.7) — Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU…

    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