CVE-2026-71488highCWE-1050CWE-407

CVE-2026-71488: high-severity vulnerability in thephpleague commonmark

league/commonmark: Quadratic-time denial of service when parsing crafted Markdown

Published · Updated

Follow this CVE+ Monitor commonmark+ Monitor php-league-commonmark

E-mail alert when it lands in KEV, gets a public PoC or its score goes up.

21Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 7.5epss 0.6%
league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 0.6.0 until 2.9.0, specially crafted Markdown lines can cause the parser to have quadratic time complexity when converting, because several parsing paths repeatedly rescan growing portions of a line to translate between character positions and byte positions, and the Autolink extension can also copy and validate the remaining line at every URL-like prefix, allowing an attacker who can submit Markdown for conversion to consume disproportionate CPU time with a comparatively small request. This issue is fixed in 2.9.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
thephpleague · commonmark
Related CVEs — thephpleague commonmark

In the same product, most dangerous first.

CVE-2026-86429HIGHcommonmark before 2.9.1 Denial of Service via SmartPunct and AttributesEPSS 0.5%CVE-2026-86434HIGHcommonmark 2.0.0 through 2.8.3 Denial of Service via Slug CollisionEPSS 0.5%CVE-2026-86433HIGHcommonmark 1.5.0 before 2.8.4 Denial of Service via AttributesEPSS 0.5%CVE-2026-86430HIGHleague/commonmark before 2.9.1 Denial of Service via parsingEPSS 0.5%CVE-2026-86428HIGHcommonmark 1.5.0 before 2.10.0 Denial of Service via AttributesEPSS 0.5%CVE-2024-58382HIGHleague/commonmark before 2.6.0 Denial of Service via Quadratic ComplexityEPSS 0.5%