{"id":"CVE-2026-27977","state":"PUBLISHED","title":"Next.js: null origin can bypass dev HMR websocket CSRF checks","description":"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, in `next dev`, cross-site protection for internal websocket endpoints could treat `Origin: null` as a bypass case even if `allowedDevOrigins` is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled content, an attacker may be able to connect to the HMR websocket channel and interact with dev websocket traffic. This affects development mode only. Apps without a configured `allowedDevOrigins` still allow connections from any origin. The issue is fixed in version 16.1.7 by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins. If upgrading is not immediately possible, do not expose `next dev` to untrusted networks and/or block websocket upgrades to `/_next/webpack-hmr` when `Origin` is `null` at the proxy.","publishedAt":"2026-03-17T23:56:24.631Z","updatedAt":"2026-03-18T19:56:16.843Z","severity":{"score":2.3,"label":"Low","version":"4.0","vector":"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","source":"GitHub_M"},"assigner":"GitHub_M","products":["vercel next.js"],"affected":[{"vendor":"vercel","product":"next.js","versions":[{"version":">= 16.0.1, < 16.1.7","status":"affected"}]}],"references":["https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36","https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a","https://github.com/vercel/next.js/releases/tag/v16.1.7"],"weaknesses":["CWE-1385"],"ingestedAt":"2026-10-29T20:11:31.369Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/27xxx/CVE-2026-27977.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-27977","state":"PUBLISHED","datePublished":"2026-03-17T23:56:24.631Z","dateUpdated":"2026-03-18T19:56:16.843Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-02-25T03:24:57.793Z"},"containers":{"cna":{"title":"Next.js: null origin can bypass dev HMR websocket CSRF checks","descriptions":[{"lang":"en","value":"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, in `next dev`, cross-site protection for internal websocket endpoints could treat `Origin: null` as a bypass case even if `allowedDevOrigins` is configured, allowing privacy-sensitive/opaque contexts (for example sandboxed documents) to connect unexpectedly. If a dev server is reachable from attacker-controlled content, an attacker may be able to connect to the HMR websocket channel and interact with dev websocket traffic. This affects development mode only. Apps without a configured `allowedDevOrigins` still allow connections from any origin. The issue is fixed in version 16.1.7 by validating `Origin: null` through the same cross-site origin-allowance checks used for other origins. If upgrading is not immediately possible, do not expose `next dev` to untrusted networks and/or block websocket upgrades to `/_next/webpack-hmr` when `Origin` is `null` at the proxy."}],"affected":[{"vendor":"vercel","product":"next.js","versions":[{"version":">= 16.0.1, < 16.1.7","status":"affected"}]}],"references":[{"url":"https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36","name":"https://github.com/vercel/next.js/security/advisories/GHSA-jcc7-9wpm-mj36","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a","name":"https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a","tags":["x_refsource_MISC"]},{"url":"https://github.com/vercel/next.js/releases/tag/v16.1.7","name":"https://github.com/vercel/next.js/releases/tag/v16.1.7","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"PASSIVE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":2.3,"baseSeverity":"LOW","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1385","lang":"en","description":"CWE-1385: Missing Origin Validation in WebSockets","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-18T00:23:47.523Z"},"source":{"advisory":"GHSA-jcc7-9wpm-mj36","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-18T19:56:08.547586Z","id":"CVE-2026-27977","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-18T19:56:16.843Z"}}]}}}