league/commonmark versions before 2.6.0 contain polynomial time complexity vulnerabilities in Markdown parsing that allow attackers to cause denial of service. Attackers can submit carefully crafted Markdown inputs designed to trigger worst-case performance, and sending multiple requests in parallel exhausts CPU resources and PHP-FPM processes.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v4.0