Cross-site scripting in mermaid - CVE-2021-43861
Published: December 29, 2021 / Updated: April 24, 2026
Vulnerability identifier: #VU127461
CSH Severity: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2021-43861
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
mermaid
mermaid
Software vendor:
mermaid-js
mermaid-js
Description
The vulnerability allows a remote attacker to execute arbitrary script code in the victim's browser.
The vulnerability exists due to cross-site scripting in the diagram rendering functionality when processing malicious diagrams. A remote attacker can supply a specially crafted diagram to execute arbitrary script code in the victim's browser.
User interaction is required to view the crafted diagram.
Remediation
Install security update from vendor's website.