Mermaid does not properly sanitize architecture diagram iconText leading to XSS
Summary
In the default configuration of mermaid 11.9.0, user supplied input for architecture diagram icons is passed to the d3 html() method, creating a sink for cross site scripting.
Details
Architecture diagram service iconText values are passed to the d3 html() method, allowing malicious users to inject arbitrary HTML and cause XSS when mermaid-js is used in it's default configuration.
The vulnerability lies here:
export const drawServices = async function (
db: ArchitectureDB,
elem: D3Element,
services: ArchitectureService[]
): Promise<number> {
for (const service of services) {
/** ... **/
} else if (service.iconText) {
bkgElem.html(
`<g>${await getIconSVG('blank', { height: iconSize, width: iconSize, fallbackPrefix: architectureIcons.prefix })}</g>`
);
const textElemContainer = bkgElem.append('g');
const fo = textElemContainer
.append('foreignObject')
.attr('width', iconSize)
.attr('height', iconSize);
const divElem = fo
.append('div')
.attr('class', 'node-icon-text')
.attr('style', `height: ${iconSize}px;`)
.append('div')
.html(service.iconText); // <- iconText passed into innerHTML
/** ... **/
};
};This issue was introduced with 734bde38777c9190a5a72e96421c83424442d4e4, around 15 months ago, which was released in v11.1.0.
PoC
Render the following diagram and observe the modified DOM.
architecture-beta
group api(cloud)[API]
service db "<img src=x onerror=\"document.write(`xss on ${document.domain}`)\">" [Database] in apiImpact
XSS on all sites that use mermaid and render user supplied diagrams without further sanitization.
Remediation
Sanitize the value of iconText before passing it to html().
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | mermaid | >= 11.1.0, < 11.10.0 | 11.10.0 |
References
- https://github.com/mermaid-js/mermaid/security/advisories/GHSA-8gwm-58g9-j8pw
- https://nvd.nist.gov/vuln/detail/CVE-2025-54880
- https://github.com/mermaid-js/mermaid/commit/2aa83302795183ea5c65caec3da1edd6cb4791fc
- https://github.com/mermaid-js/mermaid/commit/734bde38777c9190a5a72e96421c83424442d4e4
- https://github.com/mermaid-js/mermaid
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N- Weakness (CWE)
CWE-79- Platform
- npm
- Package
mermaid- Disclosed
- 19.08.2025
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-8gwm-58g9-j8pw - CC BY 4.0
Vulnerability history: mermaid
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 16
- First → latest
- 09.2020 08.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 3
- Medium 12
- Low 1
Disclosures per year
- 2020: 1
- 2021: 1
- 2022: 2
- 2023: 0
- 2024: 1
- 2025: 2
- 2026: 9
-
Mermaid does not properly sanitize architecture diagram iconText leading to XSS this entry
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