league/commonmark: Quadratic-time denial of service when parsing crafted Markdown (thephpleague commonmark)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.63 % · percentile 50 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Awaiting Analysis
Description
league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 0.6.0 until 2.9.0, specially crafted Markdown lines can cause the parser to have quadratic time complexity when converting, because several parsing paths repeatedly rescan growing portions of a line to translate between character positions and byte positions, and the Autolink extension can also copy and validate the remaining line at every URL-like prefix, allowing an attacker who can submit Markdown for conversion to consume disproportionate CPU time with a comparatively small request. This issue is fixed in 2.9.0.
Weaknesses (CWE)
- CWE-407 — Inefficient Algorithmic Complexity
- CWE-1050 — Excessive Platform Resource Consumption within a Loop
References
- https://github.com/thephpleague/commonmark/security/advisories/GHSA-2q4p-g7hv-5rgv
- https://github.com/thephpleague/commonmark/commit/a6ef6cdc308dfa39a34239c35818e75892a0e6a8
- https://github.com/thephpleague/commonmark/commit/a70979ea0d7d3377bd7127536748454a922bf5eb
- https://github.com/thephpleague/commonmark/commit/c97b02e5e652b992033b93ba5d6182f706343fc6
- https://github.com/thephpleague/commonmark/releases/tag/2.9.0
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-2q4p-g7hv-5rgv — league/commonmark: Quadratic-time denial of service when parsing crafted Markdown
European references
- ENISA EUVD · EUVD-2026-54143
- GCVE · GCVE-0-2026-71488
Affected products
| Product | Versions |
|---|---|
| thephpleague · commonmark | affected >= 0.6.0, < 2.9.0 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |