Medium [CVE-2026-59927] Denial of Service via unbounded recursion in Markdown include directive
This medium-severity Red Hat Linux advisory covers CVE-2026-59927 affecting Migration Toolkit for Applications 8, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Container Platform 4.
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Summary
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the Include directive in src/mistune/directives/include.py detects only direct self-includes and not indirect cycles, allowing two markdown files that include each other to trigger unbounded recursion, raise RecursionError, and crash the rendering request.
This issue is fixed in version 3.3.0. This oversight allows for unbounded recursion, which can lead to a `RecursionError` and crash the rendering request, resulting in a Denial of Service (DoS) for the application using the parser.
This flaw in the Mistune Include directive can cause a denial of service when an application explicitly enables the Include plugin and renders user-controlled Markdown files from disk.
Exploitation requires an attacker to place at least two coordinated Markdown files on the include search path; default Mistune configurations that parse inline strings without the Include plugin are not affected. Red Hat severity: Moderate — CVSS 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).
Weakness: CWE-835. Affected Red Hat products: Migration Toolkit for Applications 8; Red Hat OpenShift AI (RHOAI); Red Hat OpenShift Container Platform 4; Red Hat Satellite 6.
Red Hat does not currently list a fixing RHSA for this CVE.
- < 3.3.0
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
Mitigation checklist
- To mitigate this issue, Red Hat recommends avoiding the processing of untrusted Markdown content that may contain recursively linked include directives. Users should ensure that any Markdown files processed by applications utilizing Mistune are from trusted sources or are thoroughly sanitized to prevent indirect cyclic inclusions.
Official advisory · high-confidence parse· fetched 12 days ago·verify at source
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