{"id":"CVE-2026-27978","aliases":["GHSA-mq59-m269-xvcx"],"url":"https://o3.security/vulnerability/CVE-2026-27978","summary":"Next.js: null origin can bypass Server Actions CSRF checks","details":"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.","published":"2026-03-17T23:59:22.600Z","modified":"2026-08-12T03:51:44.572838446Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"next","fixedVersion":"16.1.7"}],"fix":{"url":"https://github.com/vercel/next.js/commit/a27a11d78e748a8c7ccfd14b7759ad2b9bf097d8","label":"vercel/next.js@a27a11d"},"references":[{"type":"WEB","url":"https://github.com/vercel/next.js/releases/tag/v16.1.7"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27978.json"},{"type":"ADVISORY","url":"https://github.com/vercel/next.js/security/advisories/GHSA-mq59-m269-xvcx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27978"},{"type":"FIX","url":"https://github.com/vercel/next.js/commit/a27a11d78e748a8c7ccfd14b7759ad2b9bf097d8"},{"type":"PACKAGE","url":"https://github.com/vercel/next.js"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:44.572838446Z"}}