CVE-2026-86430
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.
Scoring
- Severity
- HIGH
- CVSS base score
- 8.7
- CVSS vector
- 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
- EPSS probability
- 0.29%
- CWE
- CWE-407
- Published
- 2026-09-07
- Last modified
- 2026-09-09
Affected products
- thephpleague commonmark
- thephpleague commonmark
Weakness type
Related vulnerabilities
- CVE-2026-87822 — t-digest 3.1 through 3.3 Denial of Service via NaN Centroid Means in MergingDigest.fromBytes
- CVE-2024-58382 — league/commonmark before 2.6.0 Denial of Service via Quadratic Complexity
- CVE-2023-54395 — PocketMine-MP before 4.12.5 Denial of Service via ModalFormResponsePacket
- CVE-2026-86435 — commonmark 1.5.0 before 2.8.4 Denial of Service via Footnote
- CVE-2026-86434 — commonmark 2.0.0 through 2.8.3 Denial of Service via Slug Collision
- CVE-2026-86433 — commonmark 1.5.0 before 2.8.4 Denial of Service via Attributes
- CVE-2026-86429 — commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes
- CVE-2026-86428 — commonmark 1.5.0 before 2.10.0 Denial of Service via Attributes