Inefficient Algorithmic Complexity in markdown-it - #VU146761
Published: September 2, 2026
Vulnerability identifier: #VU146761
CSH Severity: Medium
CVSS v4: 8.7 [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]
CVE-ID: N/A
CWE-ID: CWE-407
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to inefficient algorithmic complexity in linkify handling when parsing crafted markdown input with linkify: true. A remote attacker can send specially crafted markdown content to cause a denial of service.
Only applications that enable the linkify option are vulnerable. The issue is availability-only and can block the event loop for tens of seconds with a few hundred kilobytes of ordinary-looking markdown.
Affected software
markdown-it
Remediation
Install security update from vendor's website.
markdown-it - addressed in versions 14.3.1, 15.0.1