All the vulnerabilities related to the version 11.6.0 of the package
Mermaid improperly sanitizes sequence diagram labels leading to XSS
In the default configuration of mermaid 11.9.0, user supplied input for sequence diagram labels is passed to innerHTML during calculation of element size, causing XSS.
Sequence diagram node labels with KaTeX delimiters are passed through calculateMathMLDimensions. This method passes the full label to innerHTML which allows allows malicious users to inject arbitrary HTML and cause XSS when mermaid-js is used in it's default configuration (with KaTeX support enabled).
The vulnerability lies here:
export const calculateMathMLDimensions = async (text: string, config: MermaidConfig) => {
text = await renderKatex(text, config);
const divElem = document.createElement('div');
divElem.innerHTML = text; // XSS sink, text has not been sanitized.
divElem.id = 'katex-temp';
divElem.style.visibility = 'hidden';
divElem.style.position = 'absolute';
divElem.style.top = '0';
const body = document.querySelector('body');
body?.insertAdjacentElement('beforeend', divElem);
const dim = { width: divElem.clientWidth, height: divElem.clientHeight };
divElem.remove();
return dim;
};
The calculateMathMLDimensions method was introduced in 5c69e5fdb004a6d0a2abe97e23d26e223a059832 two years ago, which was released in Mermaid 10.9.0.
Render the following diagram and observe the modified DOM.
sequenceDiagram
participant A as Alice<img src="x" onerror="document.write(`xss on ${document.domain}`)">$$\\text{Alice}$$
A->>John: Hello John, how are you?
Alice-)John: See you later!
Here is a PoC on mermaid.live: https://mermaid.live/edit#pako:eNpVUMtOwzAQ_BWzyoFKaRTyaFILiio4IK7ckA-1km1iKbaLY6spUf4dJ0AF68uOZ2dm7REqXSNQ6PHDoarwWfDGcMkUudaJGysqceLKkj3hPdl3osJ7IRvSm-qBwcCAaIXGaONRrSsnUdnobITF28PQ954lwXglai25UNNhxWAXBMyXxcGOi-3kL_5k79e73atuFSUv2HWazH1IWn0m3CC5aPf4b3p2WK--BW-4DJCOWzQ3TM0HQmiMqIFa4zAEicZv4iGMsw0D26JEBtS3NR656ywDpiYv869_11r-Ko12TQv0yLveI3eqfcjP111HUNVonrRTFuhdsVgAHWEAmuRxlG7SuEzKMi-yJAnhAjTLIk_EcbFJtuk2y9MphM8lM47KIp--AOZghtU
XSS on all sites that use mermaid and render user supplied diagrams without further sanitization.
The value of the text argument for the calculateMathMLDimensions method needs to be sanitized before getting passed on to innerHTML.
Mermaid does not properly sanitize architecture diagram iconText leading to XSS
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.
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.
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
Here is a PoC on mermaid.live: https://mermaid.live/edit#pako:eNo9T8FOwzAM_ZXI4rBJpWrpRtuIISF24caZZdKyxOsiLUnlJjCo-u9kQ8wX-_n5-dkjKK8ROEhSRxNQhUh4v8cghWMpOvKxZ7I3M3XyUc83L-9v2z9qQPo0CpneMwFPxnZsILU6M--QyNNKCAHaq2jRhfyL0vLZ7jwMiWd3443Q3krjpt38Mv4sgG3WMsi9HHDLjLs4CwcZdGQ08EARM7BISZMgjJdLBIQjWhTAU6nxIOMpCBBuSrJeug_v7b8yPdMdgR_kaUgo9loGXBvZkbS3LqHTSK8-ugC8LMrrEuAjnIEvlnlVL9q6rZu6Lh-rRQbfwKuyyZuybcvqIaWiqKcMfq6uRd7Uy-kXhYFzcA
XSS on all sites that use mermaid and render user supplied diagrams without further sanitization.
Sanitize the value of iconText before passing it to html().