CVE-2026-27978
Next.js: null origin can bypass Server Actions CSRF checks
Impact
## 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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | next | >= 16.0.1, < 16.1.7 | 16.1.7 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Vercel | Next.Js | from 16.0.1 before 16.1.7 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/vercel/next.js/commit/a27a11d78e748a8c7ccfd14b7759ad2b9bf097d8
- https://github.com/vercel/next.js/releases/tag/v16.1.7
- https://github.com/vercel/next.js/security/advisories/GHSA-mq59-m269-xvcx
- https://github.com/advisories/GHSA-mq59-m269-xvcx
- https://nvd.nist.gov/vuln/detail/CVE-2026-27978