CSRF in Vercel Next.js
CVE-2026-27978
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.
Vulnerability class: CSRF (Cross-Site Request Forgery)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (12.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 12th percentile — 12.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
- Vercel Next.js — versions >= 16.0.1, < 16.1.7
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/vercel/next.js/security/advisories/GHSA-mq59-m269-xvcx (Mitigation, Vendor Advisory)
- github.com/vercel/next.js/commit/a27a11d78e748a8c7ccfd14b7759ad2b9bf097d8 (Patch)
- github.com/vercel/next.js/releases/tag/v16.1.7 (Release Notes)
Frequently asked questions
- What is CVE-2026-27978?
- CVE-2026-27978 is a medium-severity vulnerability in Vercel Next.js, classified under Cross-Site Request Forgery (CSRF). CVSS score: 4.3/10. Published 2026-03-18.
- How severe is CVE-2026-27978?
- Medium severity. CVSS v3 base score is 4.3 out of 10.
- Is CVE-2026-27978 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.