CVE-2026-64649

Vulnerability Description

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.

CVSS Score

Affected Products

Related Weaknesses (CWE)

References

• https://github.com/vercel/next.js/commit/b51206321854193208c0805ba42acc49287f942Patch
• https://github.com/vercel/next.js/commit/e3e5666ccead3a15162793d697af5e48b7cc049Patch
• https://github.com/vercel/next.js/releases/tag/v15.5.21ProductRelease Notes
• https://github.com/vercel/next.js/releases/tag/v16.2.11ProductRelease Notes
• https://github.com/vercel/next.js/security/advisories/GHSA-89xv-2m56-2m9xMitigationVendor Advisory