PYSEC-2026-3863 Mistune: Denial of Service — RecursionError via Excessive Emphasis Markers in Markdown

Summary Mistune v3.3.2 is vulnerable to a Denial of Service DoS attack via uncontrolled recursion in the HTML rendering of deeply-nested emphasis tokens. By submitting Markdown containing approximately 1,000 consecutive asterisk characters, an attacker causes the Python process to crash with...