CVE-2026-86435
Published:September 07, 2026
Updated:September 08, 2026
commonmark versions from 1.5.0 before 2.9.0 contain a denial of service vulnerability in the Footnote extension that fails to deduplicate footnote definitions. Attackers can craft documents with duplicate footnote definitions and references to create quadratic output expansion, consuming excessive memory and CPU to exhaust server resources.
Affected Packages
https://github.com/thephpleague/commonmark.git (GITHUB):
Affected version(s) >=1.5.0 <2.9.0Fix Suggestion:
Update to version 2.9.0league/commonmark (PHP):
Affected version(s) >=1.5.0 <2.9.0Fix Suggestion:
Update to version 2.9.0Additional Notes
The description of this vulnerability differs from MITRE.
Related Resources (2)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
HIGH
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
7.5
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Weakness Type (CWE)
Inefficient Algorithmic Complexity