GHSA-3rrr-jr9j-h3q3

    Dashboard / Vulnerabilities / GHSA-3rrr-jr9j-h3q3

    GHSA-3rrr-jr9j-h3q3

    Published: 6 Aug 2026Last Modified: 10 Sept 2026

    Summary: Mermaid Architecture diagrams are vulnerable to prototype pollution

    Details: Rendering an untrusted `architecture-beta` diagram lets the diagram author write an arbitrary property with the value `horizontal` or `vertical` onto `Object.prototype`. A group id of `__proto__` is accepted as a valid parent. ### Impact Any code in the same realm that reads a property of that name from an arbitrary object, or enumerates an object with bare `for...in`, observes the injected value (which can only be the string `horizontal` or `vertical`. This may mean corrupted option/config defaults, bypassed truthiness checks, causing denial of service or logic corruption in the embedding application. Because the injected value cannot be an object or function, this is not directly exploitable for remote code execution. ### PoC ``` architecture-beta group mermaidPrototypePollutionMarker(cloud)[Marker] service a(server)[A] in __proto__ service b(server)[B] in mermaidPrototypePollutionMarker a:R -- L:b ``` The vulnerable write was introduced in commit [cb0a4703bdf01d47508bde1c08aa9a980d70bc20](https://github.com/mermaid-js/mermaid/commit/cb0a4703bdf01d47508bde1c08aa9a980d70bc20) and first shipped in `[email protected]`. The lines are unchanged in every release since. ### Patches This has been patched by https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf, released in [Mermaid v11.16.1](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1) ### Workarounds There are no known workarounds. Please update to a patched version. ### References _Are there any links users can visit to find out more?_ - https://github.com/mermaid-js/mermaid/commit/99af3fc35ef0a9a9c8c6314521344d67523ddccf - https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1

    Affected packages

    Package

    Name: mermaid

    Purl: pkg:npm/mermaid

    Affected ranges

    Type: SEMVER

    Events:

    Introduced- 11.5.0
    Fixed -11.16.1

    Affected versions

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    GHSA-3rrr-jr9j-h3q3 | CVE-DB