CVE-2025-30218
MEDIUM severity · CVSS 5.9 · Information disclosure
5.9CVSS MEDIUM
Summary
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.
Impact & exploitability
Attack vectorNetwork
Attack complexityHigh
Privileges requiredNone
User interactionNone
Confidentiality impactHigh
Integrity impactNone
Availability impactNone
Exploit probability (EPSS)0%
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Affected products we track (1)
Recommendation
Apply the vendor fix in your normal patch cycle. Open any affected product above for its exact safe version.