CVE-2026-27978: vercel next.js Cross-Site Request Forgery (CSRF)

Vulnerability summary

CVE-2026-27978 is a medium (CVSS 5.3) Cross-Site Request Forgery (CSRF) vulnerability in vercel next.js. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 13.6% of scored vulnerabilities.

Timeline

1. 17-03-2026
   PublishedVulnerability first disclosed.
2. 18-03-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-352Cross-Site Request Forgery (CSRF)The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.