league/commonmark: Denial of service in the SmartPunct and Attributes extensions — GHSA-JJV6-8J6V-6J52

Summary

### Impact Two first-party extensions contain quadratic parsing paths. Both ship with the library but must be explicitly registered on the `Environment`; neither is included in `CommonMarkConverter`, `GithubFlavoredMarkdownConverter`, or `GithubFlavoredMarkdownExtension`. **Applications that do not register `SmartPunctExtension` or `AttributesExtension` are not affected by this advisory.** **1.…

Timeline

Published by source

2026-09-01

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 7.5 out of 10.
• Review exposure for the affected product or family: composer: league/commonmark.

Product

composer: league/commonmark

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

Evidence and provenance

Canonical advisory ID

GHSA-JJV6-8J6V-6J52

Source

GitHub

Vendor

GitHub

Published by source

2026-09-01

Last source activity

2026-09-01

Curated by

hlukh.ch

Related advisories and connections

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