CVE-2026-86430
league/commonmark before 2.9.1 Denial of Service via parsing
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
league/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code block detection, reference link label lookup, and emphasis delimiter processing that perform super-linear work on crafted input. Attackers can submit specially crafted Markdown with long backtick runs, nested brackets, or delimiter sequences to consume disproportionate CPU time and prevent legitimate requests from completing.
| CWE | CWE-407 |
| Vendor | thephpleague |
| Product | commonmark |
| Published | Sep 7, 2026 |
| Last Updated | Sep 9, 2026 |
Stay Ahead of the Next One
Get instant alerts for thephpleague commonmark
Be the first to know when new high vulnerabilities affecting thephpleague commonmark are published — delivered to Slack, Telegram or Discord.
Get Free Alerts →
Free · No credit card · 60 sec setup
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 < 2.9.1
References
Credits
colinodell