https://nextjs.org/blog/cve-2025-29927 announces:
Next.js version 15.2.3 has been released to address a security vulnerability
(CVE-2025-29927). Additionally, backported patches are available.
We recommend that all self-hosted Next.js deployments using "next start" and
"output: 'standalone'" should update immediately.
Continue reading for more details on the CVE.
Timeline
2025-02-27T06:03Z: Disclosure to Next.js team via GitHub private
vulnerability reporting
2025-03-14T17:13Z: Next.js team started triaging the report
2025-03-14T19:08Z: Patch pushed for Next.js 15.x
2025-03-14T19:26Z: Patch pushed for Next.js 14.x
2025-03-17T22:44Z: Next.js 14.2.25 released
2025-03-18T00:23Z: Next.js 15.2.3 released
2025-03-18T18:03Z: CVE-2025-29927 issued by GitHub
2025-03-21T10:17Z: Security Advisory published
2025-03-22T21:21Z: Next.js 13.5.9 released
2025-03-23T06:44Z: Next.js 12.3.5 released
Vulnerability details
Next.js uses an internal header "x-middleware-subrequest" to prevent recursive
requests from triggering infinite loops. The security report showed it was
possible to skip running Middleware, which could allow requests to skip
critical checks—such as authorization cookie validation—before reaching routes.
Impact scope
Affected
Self-hosted Next.js applications using Middleware ("next start" with
"output: 'standalone'")
This affects you if you rely on Middleware for auth or security checks,
which are not then validated later in your application.
Applications using Cloudflare can turn on a Managed WAF rule
Not affected
Applications hosted on Vercel
Applications hosted on Netlify
Applications deployed as static exports (Middleware not executed)
Patched versions
For Next.js 15.x, this issue is fixed in 15.2.3
For Next.js 14.x, this issue is fixed in 14.2.25
For Next.js 13.x, this issue is fixed in 13.5.9
For Next.js 12.x, this issue is fixed in 12.3.5
If patching to a safe version is infeasible, it is recommended that you prevent
external user requests which contain the "x-middleware-subrequest" header from
reaching your Next.js application.
Our security responsibility
Next.js has published 16 security advisories since 2016. Over time, we've
continued to improve how we gather, patch, and disclose vulnerabilities.
GitHub Security Advisories and CVEs are industry-standard approaches to
notifying users, vendors, and companies of vulnerabilities in software.
While we have published a CVE, we missed the mark on partner communications.
To help us more proactively work with partners depending on Next.js, and other
infrastructure providers, we are opening a partner mailing list. Please reach
out to partn...@nextjs.org to be included.
https://github.com/vercel/next.js/security/advisories/GHSA-f82v-jwr5-mffw adds:
Credits
Allam Rachid (zhero;)
Allam Yasser (inzo_)
--
-Alan Coopersmith- alan.coopersm...@oracle.com
Oracle Solaris Engineering - https://blogs.oracle.com/solaris
