league/commonmark before 2.9.1 Denial of Service via parsing (CVE-2026-86430) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-86430

league/commonmark before 2.9.1 Denial of Service via parsing

Answer in brief

CVE-2026-86430 records a Unknown severity vulnerability in league/commonmark before 2.9.1 Denial of Service via parsing. 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.

Published Sep 7, 2026Updated Sep 7, 2026Source checked Sep 7, 2026First seen by HOL Sep 7, 2026Material review Sep 7, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

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.

Affected scope and exposure questions

The current feed maps thephpleague/commonmark (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
thephpleague/commonmarkgeneric	>=0.6.0 <2.9.1	2.9.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for thephpleague/commonmark.
Review the reported fix. Update thephpleague/commonmark to 2.9.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 7, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 7, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 7, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.