CVE-2026-27978
Next.js: null origin can bypass Server Actions CSRF checks
Description
## 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.
How to fix CVE-2026-27978
To remediate CVE-2026-27978, upgrade the affected package to a fixed version below.
- —upgrade to 16.1.7 or later
Is CVE-2026-27978 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 16.0.1, < 16.1.7
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N |