CVE-2026-86430
league/commonmark before 2.9.1 Denial of Service via parsing
- State
- Published
- Severity
- 8.7 High
- Published
- Sep 7, 2026
- Updated
- Oct 8, 2026
- Reserved
- Sep 7, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-407 Inefficient Algorithmic Complexity
Affected Products
| Product | Versions |
|---|---|
commonmarkthephpleague |
|
References
- GitHub Security Advisory (GHSA-j8pm-gj4c-rq4x)vendor-advisory
- VulnCheck Advisory: league/commonmark before 2.9.1 Denial of Service via parsingthird-party-advisory
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