CVE-2026-94486: Next.js: Information disclosure in the Next.js development server's Model Context Protocol endpoint
Next.js is a React framework for building full-stack web applications. From 16.0.0 until 16.3.8, the next dev development server exposes a Model Context Protocol endpoint without reliably restricting cross-site requests. A malicious website visited by a developer can reach the endpoint and read the project's disk location, source code snippets from error reports, route inventory, and development logs. Production deployments do not serve this endpoint. This issue is fixed in version 16.3.8.
Other sources
The Next.js development server (next dev) exposes a Model Context Protocol endpoint that does not verify which website a request originates from, allowing a malicious website visited by the developer to read sensitive development data — including the project's location on disk, source code snippets from error reports, the route inventory, and development logs. Only applications run with next dev are affected. Production deployments do not serve this endpoint.
— GitHub
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/nextto a version that resolves this vulnerability.Fixed in 16.3.8 - Upgrade
Upgrade
Next.jsto a version that resolves this vulnerability.Fixed in 16.3.8
Event History
Frequently Asked Questions
Who is exposed to this issue?
Developers running the Next.js development server with affected versions from 16.0.0 through 16.3.7 are exposed if they visit a malicious website. Production deployments are not affected because they do not serve the endpoint.
What does an attacker need to exploit it?
The attacker needs the developer to visit a malicious website while the affected next dev server is running. The malicious site can then make cross-site requests to the development server's Model Context Protocol endpoint.
What information could be disclosed?
The endpoint can expose the project's disk location, source code snippets contained in error reports, the route inventory, and development logs.
How can this be remediated?
Upgrade Next.js to version 16.3.8, which fixes the issue. The affected version range begins at 16.0.0 and ends before 16.3.8.