CVE-2026-86429 — commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes
The league/commonmark (thephpleague/commonmark) library in versions >= 1.5.0 and < 2.9.1 contains quadratic parsing complexity in its SmartPunctExtension and AttributesExtension…
Published: 2026-09-07 · CVSS: 8.7 · CVSS 4.0
The league/commonmark (thephpleague/commonmark) library in versions >= 1.5.0 and < 2.9.1 contains quadratic parsing complexity in its SmartPunctExtension and AttributesExtension. When either extension is explicitly registered on the Environment (they are not enabled by default and are excluded from the standard CommonMark and GitHub-Flavored Markdown converters), an unauthenticated attacker can submit small, specially crafted Markdown documents — such as text alternating with unpaired quotes, contiguous runs of block-level attribute blocks, or repeated class attributes — to trigger disproportionate CPU consumption and cause a denial of service. Fixed in 2.9.1.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7