Mistune: Denial of Service — RecursionError via Excessive Emphasis Markers in Markdown — GHSA-6M44-FPC8-C3RQ

Summary

## 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 RecursionError. ## Details The InlineParser's _process_emphasis_delimiters() creates deeply nested <strong> tokens from…

Timeline

Published by source

2026-09-02

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 7.5 out of 10.
• Reported EPSS value: 0.00278.
• Review exposure for the affected product or family: pip: mistune.

Product

pip: mistune

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-6M44-FPC8-C3RQ

Source

GitHub

Vendor

GitHub

Published by source

2026-09-02

Last source activity

2026-09-02

Additional identifiers

CVE-2026-76098

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.