Summary
Next.js: Unauthenticated disclosure of internal Server Function endpoints
Workarounds
Never assume any authentication claims at the use cache or use server boundary. Always authenticate within the boundary.
Impact
In Next.js applications using App Router, Server Actions (use server) or use cache endpoints can be disclosed bypassing any authentication on the pages where these endpoints are usually used.
Server Action IDs can be disclosed to unauthenticated users via publicly served client artifacts (for example, static chunks containing action references).
Affected users are applications using App Router + Server Actions.
By itself, this disclosure is typically a recon/enumeration primitive; however, it can increase risk when combined with other weaknesses.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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next to 15.5.21 or later; next to 16.2.11 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-64643? CVE-2026-64643 is a medium-severity security vulnerability in next (npm), affecting versions >= 13.0.0, < 15.5.21. It is fixed in 15.5.21, 16.2.11.
- Which versions of next are affected by CVE-2026-64643? next (npm) versions >= 13.0.0, < 15.5.21 is affected.
- Is there a fix for CVE-2026-64643? Yes. CVE-2026-64643 is fixed in 15.5.21, 16.2.11. Upgrade to this version or later.
- Is CVE-2026-64643 exploitable, and should I be worried? Whether CVE-2026-64643 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-64643 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-64643?
- Upgrade
nextto 15.5.21 or later - Upgrade
nextto 16.2.11 or later
- Upgrade