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wid-sec-w-2026-0748  ·  Published 2026-03-16  ·  View on BSI CERT-Bund ↗

Vercel Next.js: Multiple Vulnerabilities

CVSS 6.9 MEDIUM

Risk Summary

Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, `origin: null` was treated as a "missing" origin during Server Action CSRF validation. As a result, requests from opaque contexts (such as sandboxed iframes) could bypass origin verification instead of being validated as cross-origin requests. An attacker could induce a victim browser to submit Server Actions from a sandboxed context, potentially executing state-changing actions with victim credentials (CSRF). This is fixed in version 16.1.7 by treating `'null'` as an explicit origin value and enforcing host/origin checks unless `'null'` is explicitly allowlisted in `experimental.serverActions.allowedOrigins`. If upgrading is not immediately possible, add CSRF tokens for sensitive Server Actions, prefer `SameSite=Strict` on sensitive auth cookies, and/or do not allow `'null'` in `serverActions.allowedOrigins` unless intentionally required and additionally protected.

Affected Vendors

Vercel

Affected Products (4)

Vercel · Next.js <16.1.7
Vercel · Next.js 16.1.7
Vercel · Next.js <15.5.13
Vercel · Next.js 15.5.13

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