CVE-2026-59928 [HIGH] – Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown

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.