Medium [CVE-2026-59925] Denial of Service via crafted Markdown input
This medium-severity Red Hat Linux advisory covers CVE-2026-59925 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, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.
An attacker can exploit this vulnerability by providing specially crafted Markdown input containing long sequences of emphasis pairs. This can cause the parser to perform excessive computational work, leading to a denial of service (DoS) condition in the default Mistune parsing.
This can lead to resource exhaustion and service unavailability in applications utilizing Mistune, where user-controlled Markdown input is processed.
Red Hat assigns PR:L in the product-specific CVSS base score because delivering the crafted Markdown document to Mistune requires authenticated access in affected products; platform login and RBAC prevent unauthenticated remote submission in default deployments.
The upstream PR:N score assumes any Internet-facing application parsing untrusted Markdown without authentication. Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-1333.
- < 3.3.0
Official advisory · high-confidence parse· fetched 10 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 10 days ago·verify at source
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