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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-71488
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-06 22:18:31 UTC
Updated2026-08-06 22:18:31 UTC
Descriptionleague/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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

Problem Types: CWE-407 | CWE-1050 | CWE-407 CWE-407: Inefficient Algorithmic Complexity | CWE-1050 CWE-1050: Excessive Platform Resource Consumption within a Loop

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Thephpleague Commonmark affected >= 0.6.0, < 2.9.0 Not specified

References

ReferenceSourceLinkTags
github.com/thephpleague/commonmark/commit/a70979ea0d7d3377bd712753674845... [email protected] github.com
github.com/thephpleague/commonmark/commit/c97b02e5e652b992033b93ba5d6182... [email protected] github.com
github.com/thephpleague/commonmark/commit/a6ef6cdc308dfa39a34239c35818e7... [email protected] github.com
github.com/thephpleague/commonmark/releases/tag/2.9.0 [email protected] github.com
github.com/thephpleague/commonmark/security/advisories/GHSA-2q4p-g7hv-5rgv [email protected] github.com
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