Next.js development server exposes MCP endpoint to CSRF attacks

The Next.js development server's Model Context Protocol endpoint lacks origin verification, allowing malicious websites to access sensitive development data including source code and project paths. Only development builds are affected.

Disclosed 7 October 2026 · Record updated 7 October 2026

Impact

Developers running next dev could have sensitive development data including source code snippets, project location, route inventory, and development logs exposed to malicious websites they visit

Our coverage

A developer's workshop lies open at night, blueprints scattered across tables as a stranger walks through the unlocked door, casually photographing every design and specification inside.

Vulnerabilities

Next.js dev server leaks source code through open MCP endpoint

A GitHub advisory published on 7 October 2026 says Vercel's Next.js development server serves a Model Context Protocol endpoint that any website can query.

7 Oct 2026

Sources

github.comhttps://github.com/advisories/GHSA-39w2-rjm5-chcv