Vulnerability Details 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 4.3%
CVSS Severity
CVSS v3 Score 4.3
References
Products affected by CVE-2026-27978
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cpe:2.3:a:vercel:next.js:16.0.1
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cpe:2.3:a:vercel:next.js:16.0.10
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cpe:2.3:a:vercel:next.js:16.0.2
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cpe:2.3:a:vercel:next.js:16.0.3
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cpe:2.3:a:vercel:next.js:16.0.4
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cpe:2.3:a:vercel:next.js:16.0.5
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cpe:2.3:a:vercel:next.js:16.0.6
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cpe:2.3:a:vercel:next.js:16.0.7
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cpe:2.3:a:vercel:next.js:16.0.8
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cpe:2.3:a:vercel:next.js:16.0.9
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cpe:2.3:a:vercel:next.js:16.1.0
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cpe:2.3:a:vercel:next.js:16.1.1
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cpe:2.3:a:vercel:next.js:16.1.2
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cpe:2.3:a:vercel:next.js:16.1.3
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cpe:2.3:a:vercel:next.js:16.1.4
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cpe:2.3:a:vercel:next.js:16.1.5
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cpe:2.3:a:vercel:next.js:16.1.6