Answer in brief
CVE-2026-86429 records a Unknown severity vulnerability in commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes. The current sources do not mark it as known exploited. The current feed maps thephpleague/commonmark (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps thephpleague/commonmark (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| thephpleague/commonmarkgeneric | >=1.5.0 <2.9.1 | 2.9.1 |
Published upstream
Sep 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 7, 2026
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.
Quoted source text, attributed separately from HOL analysis.