CVE-2026-86428

High

Description

commonmark versions from 1.5.0 before 2.10.0 contain a denial of service vulnerability in the AttributesExtension when processing distinctly-named attributes. Attackers can submit Markdown with numerous distinct attribute names to cause quadratic-time attribute merging and filtering, consuming disproportionate CPU resources and preventing 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 commonmark2.10.0 or later
league/commonmark2.10.0 or later

Vendor advisories

github.com/thephpleague/commonmark/security/advisories/GHSA-8rr7-cvq3-gmfh

Affected products

Product	Affected versions	Fixed in
thephpleague commonmark	1.5.0 ≤ v < 2.10.0	2.10.0
league/commonmarkPackagist	1.5.0 ≤ v < 2.10.0	2.10.0

Check your version

Choose the product and enter the version you run to see whether it falls in the affected range.

In the Intelligence 360 plan

Attack Surface Management

See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.