Next.js: Unauthenticated disclosure of internal Server Function endpoints (CVE-2026-64643) | HOL Guard CVE

Medium severityCVE-2026-64643GHSA-955P-X3MX-JCVP

Next.js: Unauthenticated disclosure of internal Server Function endpoints

Answer in brief

CVE-2026-64643 records a Medium severity vulnerability in Next.js: Unauthenticated disclosure of internal Server Function endpoints. The current sources do not mark it as known exploited. The current feed maps next (npm), next (npm), next (npm), next (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 21, 2026Updated Jul 23, 2026Source checked Aug 24, 2026First seen by HOL Aug 8, 2026Material review Jul 23, 2026

Upstream Advisory

Key facts

Risk: Medium
Exploitation: Not marked as known exploited
Affected software: 4 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps next (npm), next (npm), next (npm), next (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
nextnpm	>=13.0.0 <15.5.21	15.5.21
nextnpm	>=16.0.0 <16.2.11	16.2.11
nextnpm	>=13.0.0<15.5.21	Not reported
nextnpm	>=16.0.0<16.2.11	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for next, next, next.
Review the reported fix. Update next to 15.5.21; next to 16.2.11 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 21, 2026
Evidence: source:ghsa:source_dates:source-dates:record
Source modified
Jul 23, 2026
Evidence: source:ghsa:source_dates:source-dates:record
First seen by HOL
Aug 8, 2026

Sources and claim methodology

Upstream source description

## 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. ## Workarounds Never assume any authentication claims at the `use cache` or `use server` boundary. Always authenticate within the boundary.

Quoted source text, attributed separately from HOL analysis.