{"id":"GHSA-jcc7-9wpm-mj36","summary":"Next.js: null origin can bypass dev HMR websocket CSRF checks","details":"## Summary\nIn `next dev`, cross-site protections for internal development endpoints could treat `Origin: null` as a bypass case even when [`allowedDevOrigins`](https://nextjs.org/docs/app/api-reference/config/next-config-js/allowedDevOrigins) is configured. This could allow privacy-sensitive or opaque browser contexts, such as sandboxed documents, to access privileged internal dev-server functionality unexpectedly.\n\n## Impact\nIf a developer visits attacker-controlled content while running an affected `next dev` server with [`allowedDevOrigins`](https://nextjs.org/docs/app/api-reference/config/next-config-js/allowedDevOrigins) configured, attacker-controlled browser code may be able to connect to internal development endpoints and interact with sensitive dev-server functionality that should have remained blocked.\n\nThis issue affects development mode only. It does not affect `next start`, and it does not expose internal debugging functionality to the network by default.\n\n## Patches\nFixed by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins on internal development endpoints.\n\n## Workarounds\nIf upgrade is not immediately possible:\n- Do not expose `next dev` to untrusted networks.\n- If you use [`allowedDevOrigins`](https://nextjs.org/docs/app/api-reference/config/next-config-js/allowedDevOrigins), reject requests and websocket upgrades with `Origin: null` for internal dev endpoints at your proxy.","aliases":["CVE-2026-27977"],"modified":"2026-03-25T19:50:24.668371Z","published":"2026-03-17T15:29:48Z","database_specific":{"severity":"LOW","github_reviewed":true,"github_reviewed_at":"2026-03-17T15:29:48Z","nvd_published_at":"2026-03-18T00:16:19Z","cwe_ids":["CWE-1385"]},"references":[{"type":"WEB","url":"https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27977"},{"type":"WEB","url":"https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a"},{"type":"PACKAGE","url":"https://github.com/vercel/next.js"},{"type":"WEB","url":"https://github.com/vercel/next.js/releases/tag/v16.1.7"}],"affected":[{"package":{"name":"next","ecosystem":"npm","purl":"pkg:npm/next"},"ranges":[{"type":"SEMVER","events":[{"introduced":"16.0.1"},{"fixed":"16.1.7"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-jcc7-9wpm-mj36/GHSA-jcc7-9wpm-mj36.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"}]}