CVE-2026-86430
High
Description
league/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code block detection, reference link label lookup, and emphasis delimiter processing that perform super-linear work on crafted input. Attackers can submit specially crafted Markdown with long backtick runs, nested brackets, or delimiter sequences to consume disproportionate CPU time and prevent legitimate requests from completing.
SeverityHigh
CVSS7.5
Exploit probability—
ProductThephpleague Commonmark
PublishedSep 7, 2026
First seenSep 7, 2026
Weakness typeCWE-407CWE-407
How to fix
Update
- thephpleague commonmark2.9.1 or later
- league/commonmark2.9.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| thephpleague commonmark | v < 2.9.1 | 2.9.1 |
| league/commonmarkPackagist | 0.6.0 ≤ v < 2.9.1 | 2.9.1 |
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