Next.js may leak x-middleware-subrequest-id to external hosts
Summary
Next.js may leak x-middleware-subrequest-id to external hosts
Original description
The description as published by the source.
Next.js is a React framework for building full-stack web applications. To mitigate CVE-2025-29927, Next.js validated the x-middleware-subrequest-id which persisted across multiple incoming requests. However, this subrequest ID is sent to all requests, even if the destination is not the same host as the Next.js application. Initiating a fetch request to a third-party within Middleware will send the x-middleware-subrequest-id to that third party. This vulnerability is fixed in 12.3.6, 13.5.10, 14.2.26, and 15.2.4.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- web vercel.com