CVE-2026-71488

HIGH 7.5

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

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-407 CWE-1050
Vendor	thephpleague
Product	commonmark
Published	Aug 6, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

thephpleague / commonmark

>= 0.6.0, < 2.9.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/thephpleague/commonmark/security/advisories/GHSA-2q4p-g7hv-5rgv github.com: https://github.com/thephpleague/commonmark/commit/a6ef6cdc308dfa39a34239c35818e75892a0e6a8 github.com: https://github.com/thephpleague/commonmark/commit/a70979ea0d7d3377bd7127536748454a922bf5eb github.com: https://github.com/thephpleague/commonmark/commit/c97b02e5e652b992033b93ba5d6182f706343fc6 github.com: https://github.com/thephpleague/commonmark/releases/tag/2.9.0