CVE-2026-71437

Name	CVE-2026-71437
Description	Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. From version 11.5.0 until 11.16.1, Mermaid Architecture Diagrams are vulnerable to prototype pollution when a diagram defines a group with an id of __proto__. Because the group id is used directly as an object property key without validation, an attacker who can supply diagram text can pollute Object.prototype, potentially affecting the behavior of the embedding application. This issue is fixed in version 11.16.1.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
node-mermaid (PTS)	bullseye	8.7.0+ds+~cs27.17.17-3+deb11u2	vulnerable
	forky	9.2.2+~2.0.0-1	vulnerable
	sid	9.2.2+~2.0.0-2	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
node-mermaid	source	(unstable)	(unfixed)

Notes

https://github.com/mermaid-js/mermaid/security/advisories/GHSA-3rrr-jr9j-h3q3
Fixed by: https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf (mermaid@11.16.1)
check introducing commit for further assessment