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Vulnerability · Published Jul 27, 2026 · Assigned by GitHub_M

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

Medium 6.3

In plain English

A medium-severity security flaw in next.js from vercel. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.5%top 56.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
npmnext15.5.21GHSA-955p-x3mx-jcvp
npmnext16.2.11GHSA-955p-x3mx-jcvp

Affected products (as reported)

VendorProductVersions
vercel next.js >= 13.0.0, < 15.5.21>= 16.0.0, < 16.2.11

Weakness: CWE-201 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

References