Medium [CVE-2026-59928] Denial of Service via crafted Markdown document with reference-link definitions
This medium-severity Red Hat Linux advisory covers CVE-2026-59928 affecting Migration Toolkit for Applications 8, Red Hat OpenShift AI (RHOAI), Red Hat OpenShift Container Platform 4.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Summary
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. A remote attacker could exploit this vulnerability by providing a specially crafted Markdown document containing numerous repeated or distinct reference-link definitions.
This can lead to excessive processing, causing CPU exhaustion and a denial of service (DoS) for the affected system. This triggers excessive CPU consumption during parsing, which may render affected applications unresponsive and result in a denial of service.
Red Hat uses PR:L because delivering the crafted Markdown document document to Mistune will require authenticated access in affected products, platform login/RBAC prevents unauthenticated remote submission in default deployments. The upstream PR:N score assumes any Internet-facing app 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-606.
Affected Red Hat products: Migration Toolkit for Applications 8; Red Hat OpenShift AI (RHOAI); Red Hat OpenShift Container Platform 4; Red Hat Satellite 6.
Is CVE-2026-59928 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-59928 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-59928?
Upgrade to a fixed release named by Red Hat:
- 3.3.0
Confirm against the vendor advisory before you patch.
- < 3.3.0
Official advisory · high-confidence parse· fetched 11 days ago·verify at source
Mitigation checklist
- To mitigate this issue, avoid processing untrusted Markdown documents with affected Red Hat products. Restricting the input sources to trusted content can reduce the risk of a denial of service attack.
Official advisory · high-confidence parse· fetched 11 days ago·verify at source
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