CVE-2026-71488

HighCVSS 7.5

Published: 06/08/2026(UTC)Updated: 07/08/2026(UTC)Translated: 07/08/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.35%

27th percentile - higher than 27% of all known CVEs

Summary

Vulnerability in the PHP library league/commonmark (versions 0.6.0 to 2.9.0) causes quadratic time complexity when parsing specially crafted Markdown lines. An attacker can submit a small request that consumes disproportionate CPU time.

Risk Assessment

May lead to server overload and denial of service, especially in applications processing user input.

Recommendation

Update league/commonmark to version 2.9.0 or later.

Other vulnerabilities in league/commonmark

CVE-2026-71478Medium
league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the AttributesExtension's href and src unsafe-link filter can be bypassed by embedding control bytes, such as a tab, carriage return, line feed, or leading C0 control character, in a javascript: URL that browsers discard before parsing the scheme, causing the browser to still execute the script even when the unsafe-link filter is enabled. This issue is fixed in 2.9.0.

Original NVD description (English source)

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.