CVE-2026-86429 Details
Description
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.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Sep 18, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/thephpleague/commonmark/security/advisories/GHSA-jjv6-8j6v-6j52 | [email protected] | MitigationVendor Advisory |
| https://www.vulncheck.com/advisories/commonmark-before-2.9.1-denial-of-service-via-smartpunct-and-attributes | [email protected] | Third Party Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-407 | Inefficient Algorithmic Complexity | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| thephpleague commonmark | >= 1.5.0, < 2.9.1 |
CPE
Remediation
| |
Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 19, 2026 | CVE Modified | CISA-ADP |
| Sep 9, 2026 | Initial Analysis | [email protected] |
| Sep 7, 2026 | New CVE Received | [email protected] |