CVE-2026-59928 — Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions
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 quadra…
Published: 2026-07-08 · CVSS: 7.5 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7