Security Advisory: CVE-2025-66478 (Next.js App Router RCE)
Key Points
- CVSS 10.0 RCE via React Server Components
- Upgrade Next.js to patched releases immediately
- Run npx fix-react2shell-next and rotate secrets
Summary
A critical vulnerability in the React Server Components (RSC) protocol (originating from React CVE-2025-55182) allows remote code execution (CVSS 10.0) when processing attacker-controlled requests in unpatched Next.js applications that use the App Router. This advisory (CVE-2025-66478) tracks the downstream Next.js impact and required remediation. There is no workaround — upgrade immediately and rotate secrets after redeploy.
Key Points
- Impact: Remote code execution in Next.js App Router apps using RSC under specific request conditions.
- Affected: Next.js 15.x, 16.x, and Next.js 14.3.0-canary.77 and later canary releases when using the App Router with RSC.
- Not affected: Next.js 13.x (stable), Next.js 14.x stable, Pages Router apps, and Edge Runtime.
- Severity: CVSS 10.0. Immediate patching required; rotate secrets after patch & redeploy.
Affected versions
- Next.js 15.x
- Next.js 16.x
- Next.js 14.3.0-canary.77 and later canary releases (if using App Router + RSC)
Patched versions (upgrade to the appropriate release line)
- 15.0.5, 15.1.9, 15.2.6, 15.3.6, 15.4.8, 15.5.7
- 16.0.7
- Canary fixes: 15.6.0-canary.58, 16.1.0-canary.12
- If on 14.3.0-canary.77 or later canary: downgrade to the latest stable 14.x (
npm install next@14) or move to a patched 15/16 release.
Immediate actions (practical steps)
- Identify affected deployments running App Router with RSC and check Next.js versions.
- Upgrade to the patched release for your release line, for example:
npm install next@15.0.5(or the matching patched version for your 15.x line)npm install next@16.0.7(for 16.0.x)npm install next@15.6.0-canary.58/npm install next@16.1.0-canary.12(canary fixes)
- Run the provided interactive tool to check and apply deterministic bumps:
npx fix-react2shell-next. - Redeploy and then rotate all environment secrets (API keys, credentials, tokens), starting with highest-privilege secrets.
- There is no workaround; patching is required.
Notes & resources
- This advisory intentionally limits technical detail to reduce risk to unpatched deployments.
- See the Next.js advisory and React advisory for additional context, and the
npx fix-react2shell-nextGitHub repo for automated assistance. - Disclosure credit: Lachlan Davidson (responsible disclosure).