{"id":"CVE-2026-27977","summary":"Next.js: null origin can bypass dev HMR websocket 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, 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.","aliases":["GHSA-jcc7-9wpm-mj36"],"modified":"2026-08-12T03:51:24.092770610Z","published":"2026-03-17T23:56:24.631Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-1385"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27977.json"},"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-2026-27977.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/vercel/next.js/commit/862f9b9bb41d235e0d8cf44aa811e7fd118cee2a"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/vercel/next.js","events":[{"introduced":"e08402bfad8db05b0df820daf4f08c9c65ab1f7b"},{"fixed":"bdf3e3577a6d55ea186a48238d61fbd8da07a626"},{"fixed":"862f9b9bb41d235e0d8cf44aa811e7fd118cee2a"}],"database_specific":{"cpe":"cpe:2.3:a:vercel:next.js:*:*:*:*:*:node.js:*:*","extracted_events":[{"introduced":"16.0.1"},{"fixed":"16.1.7"}],"source":["CPE_RANGE","REFERENCES"]}}],"versions":["v16.2.0-canary.101","v16.2.0-canary.100","v16.2.0-canary.99","v16.2.0-canary.98","v16.2.0-canary.97","v16.2.0-canary.96","v16.2.0-canary.95","v16.2.0-canary.94","v16.2.0-canary.93","v16.2.0-canary.92","v16.2.0-canary.91","v16.2.0-canary.90","v16.2.0-canary.89","v16.2.0-canary.88","v16.2.0-canary.87","v16.2.0-canary.86","v16.2.0-canary.85","v16.2.0-canary.84","v16.2.0-canary.83","v16.2.0-canary.82","v16.2.0-canary.81","v16.2.0-canary.78","v16.2.0-canary.80","v16.2.0-canary.79","v16.2.0-canary.77","v16.2.0-canary.76","v16.2.0-canary.75","v16.2.0-canary.74","v16.2.0-canary.71","v16.2.0-canary.73","v16.2.0-canary.69","v16.2.0-canary.72","v16.2.0-canary.70","v16.2.0-canary.68","v16.2.0-canary.67","v16.2.0-canary.66","v16.2.0-canary.65","v16.2.0-canary.64","v16.2.0-canary.63","v16.2.0-canary.62","v16.2.0-canary.61","v16.2.0-canary.60","v16.2.0-canary.59","v16.2.0-canary.58","v16.2.0-canary.57","v16.2.0-canary.56","v16.2.0-canary.55","v16.2.0-canary.54","v16.2.0-canary.53","v16.2.0-canary.52","v16.2.0-canary.51","v16.2.0-canary.50","v16.2.0-canary.49","v16.2.0-canary.48","v16.2.0-canary.47","v16.2.0-canary.46","v16.2.0-canary.45","v16.2.0-canary.44","v16.2.0-canary.43","v16.2.0-canary.42","v16.2.0-canary.41","v16.2.0-canary.40","v16.2.0-canary.39","v16.2.0-canary.38","v16.2.0-canary.37","v16.2.0-canary.36","v16.2.0-canary.35","v16.2.0-canary.34","v16.2.0-canary.33","v16.2.0-canary.32","v16.2.0-canary.31","v16.2.0-canary.30","v16.2.0-canary.29","v16.2.0-canary.28","v16.2.0-canary.27","v16.2.0-canary.26","v16.2.0-canary.25","v16.2.0-canary.24","v16.2.0-canary.23","v16.2.0-canary.22","v16.2.0-canary.21","v16.2.0-canary.20","v16.2.0-canary.19","v16.2.0-canary.18","v16.2.0-canary.17","v16.1.6","v16.2.0-canary.16","v16.2.0-canary.15","v16.2.0-canary.14","v16.1.5","v16.2.0-canary.11","v16.2.0-canary.13","v16.2.0-canary.12","v16.2.0-canary.10","v16.2.0-canary.9","v16.2.0-canary.8","v16.2.0-canary.7","v16.2.0-canary.6","v16.2.0-canary.5","v16.1.4","v16.2.0-canary.4","v16.2.0-canary.3","v16.2.0-canary.2","v16.2.0-canary.1","v16.2.0-canary.0","v16.1.1-canary.36","v16.1.1-canary.35","v16.1.1-canary.34","v16.1.3","v16.1.1-canary.33","v16.1.1-canary.32","v16.1.1-canary.30","v16.1.1-canary.31","v16.1.2","v16.1.1-canary.29","v16.1.1-canary.28","v16.1.1-canary.27","v16.1.1-canary.26","v16.1.1-canary.25","v16.1.1-canary.24","v16.1.1-canary.23","v16.1.1-canary.22","v16.1.1-canary.21","v16.1.1-canary.20","v16.1.1-canary.19","v16.1.1","v16.1.1-canary.18","v16.1.1-canary.17","v16.1.1-canary.16","v16.1.1-canary.15","v16.1.1-canary.14","v16.1.1-canary.13","v16.1.1-canary.12","v16.1.1-canary.11","v16.1.1-canary.10","v16.1.1-canary.9","v16.1.1-canary.8","v16.1.1-canary.7","v16.1.1-canary.6","v16.1.1-canary.5","v16.1.1-canary.4","v16.1.0","v16.1.1-canary.3","v16.1.1-canary.2","v16.1.1-canary.1","v16.1.1-canary.0","v16.1.0-canary.34","v16.1.0-canary.33","v16.1.0-canary.32","v16.1.0-canary.31","v16.1.0-canary.30","v16.1.0-canary.29","v16.1.0-canary.28","v16.1.0-canary.27","v16.1.0-canary.26","v16.1.0-canary.25","v16.1.0-canary.24","v16.1.0-canary.23","v16.1.0-canary.22","v16.1.0-canary.21","v16.1.0-canary.20","v16.1.0-canary.19","v16.1.0-canary.18","v16.1.0-canary.17","v16.1.0-canary.16","v16.1.0-canary.15","v16.1.0-canary.14","v16.1.0-canary.13","v16.1.0-canary.11","v16.1.0-canary.12","v16.1.0-canary.10","v16.1.0-canary.9","v16.1.0-canary.8","v16.1.0-canary.7","v16.1.0-canary.4","v16.1.0-canary.6","v16.1.0-canary.5","v16.1.0-canary.3","v16.1.0-canary.2","v16.1.0-canary.1","v16.1.0-canary.0","v16.0.2-canary.34","v16.0.2-canary.33","v16.0.2-canary.32","v16.0.2-canary.31","v16.0.2-canary.30","v16.0.2-canary.29","v16.0.2-canary.28","v16.0.2-canary.27","v16.0.2-canary.26","v16.0.2-canary.25","v16.0.2-canary.24","v16.0.2-canary.2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