CVE-2026-64649: Vercel Next.js

Medium severity, CVSS 6.5. EPSS: 0.5% chance of exploitation in the next 30 days.

Next.js is a React framework for building full-stack web applications. In versions 14.1.1 through 15.5.20 and 16.0.0 through 16.2.10, when a Server Action forwards or redirects a request, an attacker can cause the server to send that outbound request to a malicious host (Server-Side Request Forgery). This requires the attacker's request to control Host-associated headers. In some configurations, it's also possible to obtain internal values that weaken middleware/proxy authorization. Applications that use Server Actions are affected when the incoming host header is not fixed to a trusted value. This typically occurs on custom servers, or on deployments not behind a proxy that pins the host. Managed hosting pins the host upstream and is not affected; next start and standalone output do the same from version 14.2 onward. This issue has been fixed in versions 15.5.21 and 16.2.11.

Affected products

• Vercel Next.js: from 14.1.1, before 15.5.21 (fixed in 15.5.21); from 16.0.0, before 16.2.11 (fixed in 16.2.11)

Published 2026-07-27. Last modified 2026-07-29.