Vulnerability 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/thephpleague/commonmark/commit/a6ef6cdc308dfa39a34239c35818e7
- https://github.com/thephpleague/commonmark/commit/a70979ea0d7d3377bd712753674845
- https://github.com/thephpleague/commonmark/commit/c97b02e5e652b992033b93ba5d6182
- https://github.com/thephpleague/commonmark/releases/tag/2.9.0
- https://github.com/thephpleague/commonmark/security/advisories/GHSA-2q4p-g7hv-5r
FAQ
What is CVE-2026-71488?
CVE-2026-71488 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 c...
How severe is CVE-2026-71488?
CVE-2026-71488 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-71488?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.