GHSA-8gwm-58g9-j8pw
Mermaid does not properly sanitize architecture diagram iconText leading to XSS
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
mermaidnpmDescription
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 api
Impact
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | mermaid | ≥ 11.1.0&&< 11.10.0 | 11.10.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mermaid. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update mermaid to 11.10.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8gwm-58g9-j8pw is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-8gwm-58g9-j8pw is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-8gwm-58g9-j8pw. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-8gwm-58g9-j8pw in your dependencies?
O3 detects GHSA-8gwm-58g9-j8pw across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.