# CVE-2026-64643: Next.js: Unauthenticated Disclosure of Internal Server Function endpoints

- Exploited (CISA KEV): no
- Published: 2026-07-27
- CVSS: 6.3 MEDIUM (v4.0)
- EPSS: 0.5% (44th percentile)
- CWE: CWE-201

Next.js is a React framework for building full-stack web applications. In versions 12.0.0 through 15.5.20 and 16.0.0 through 16.2.10, 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 and Server Actions. By itself, this disclosure is typically a recon/enumeration primitive; however, it can increase risk when combined with other weaknesses. This issue has been fixed in versions 15.5.21 and 16.2.11.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Blocks by default | 2026-07-21 | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | No public claim | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### Cloudflare

- 2026-07-21 · updated · rule 6c4135d4d9d745e4866ad83672952826 · default Block
  > Next.js - Information Disclosure - CVE-2026-64643. Previous action: N/A. New action: Block. This was labeled as Generic Rules - Information Disclosure.
  Source: https://developers.cloudflare.com/changelog/post/2026-07-21-waf-release/

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2026-64643 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-64643