What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-27 · updated 2026-10-24
• Weakness: CWE-201

Description

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.

Affected products

• Next.js: from 13.0.0 before 15.5.21; from 16.0.0 before 16.2.11 — fixed in 15.5.21, 16.2.11
• Npm Next: from 13.0.0 before 15.5.21; from 16.0.0 before 16.2.11 — fixed in 15.5.21, 16.2.11

How to fix

Upgrade to a fixed version: Next.js 15.5.21, 16.2.11; Npm Next 15.5.21, 16.2.11. Check the vendor advisory for mitigations.

References

• https://github.com/vercel/next.js/commit/1b0c3ae912a3ad925c60065cc8d55b070fa8bcd3
• https://github.com/vercel/next.js/commit/ff12a6124e1504f17b62de948b8a553fdecaef7b
• https://github.com/vercel/next.js/releases/tag/v15.5.21
• https://github.com/vercel/next.js/releases/tag/v16.2.11
• https://github.com/vercel/next.js/security/advisories/GHSA-955p-x3mx-jcvp

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