MediumGHSA-mq59-m269-xvcxCVE-2026-27978

Next.js: null origin can bypass Server Actions CSRF checks

Published 17 Mar 2026 · Updated 19 Mar 2026

Affected package

nextnpm
Affected
>=16.0.1 <16.1.7
Fixed in
16.1.7
Update to the fixed version for your release line, for example:npm install next@16.1.7

Details

Summary

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.

Impact

An attacker could induce a victim browser to submit Server Actions from a sandboxed context, potentially executing state-changing actions with victim credentials (CSRF).

Patches

Fixed by treating 'null' as an explicit origin value and enforcing host/origin checks unless 'null' is explicitly allowlisted in experimental.serverActions.allowedOrigins.

Workarounds

If upgrade is not immediately possible:

  • Add CSRF tokens for sensitive Server Actions.
  • Prefer SameSite=Strict on sensitive auth cookies.
  • Do not allow 'null' in serverActions.allowedOrigins unless intentionally required and additionally protected.

Is GHSA-mq59-m269-xvcx in any of your client repos?

Checking one package by hand is fine. Checking it across forty client projects is not. NPMscan reads the lockfiles in every GitHub repo you pick, finds each project with an affected next, and gives you the command that fixes it.

Scan a project free, no signupOr connect GitHub to scan every repo

References

Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.