Vulnerability · Published Aug 6, 2026 · Assigned by GitHub_M
CVE-2026-71437Mermaid Architecture diagrams are vulnerable to prototype pollution
Medium 6.5
In plain English
A medium-severity prototype pollution in mermaid from mermaid-js. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | node-mermaid | no fix listed | DEBIAN-CVE-2026-71437 |
| Ubuntu:22.04:LTS | node-mermaid | no fix listed | UBUNTU-CVE-2026-71437 |
| Ubuntu:26.10 | node-mermaid | no fix listed | UBUNTU-CVE-2026-71437 |
| npm | mermaid | 11.16.1 | GHSA-3rrr-jr9j-h3q3 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| mermaid-js | mermaid | >= 11.5.0, < 11.16.1 |
Weakness: CWE-1321 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:H/SI:H/SA:H
References
- https://github.com/mermaid-js/mermaid/security/advisories/GHSA-3rrr-jr9j-h3q3 x_refsource_CONFIRM
- https://github.com/mermaid-js/mermaid/pull/8022 x_refsource_MISC
- https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf x_refsource_MISC
- https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1 x_refsource_MISC