{"id":"CVE-2026-64643","aliases":["GHSA-955p-x3mx-jcvp"],"title":"Next.js: Unauthenticated disclosure of internal Server Function endpoints","summary":"Next.js: Unauthenticated disclosure of internal Server Function endpoints","severity":"medium","cwe":["CWE-201"],"vendor":"next","product":"next","ecosystem":"npm","affected":["next >= 13.0.0, < 15.5.21","next >= 16.0.0, < 16.2.11"],"patched":["next 15.5.21","next 16.2.11"],"published":"2026-07-22","updated":"2026-07-22","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-955p-x3mx-jcvp","references":[{"url":"https://github.com/vercel/next.js/security/advisories/GHSA-955p-x3mx-jcvp"},{"url":"https://github.com/vercel/next.js/commit/1b0c3ae912a3ad925c60065cc8d55b070fa8bcd3"},{"url":"https://github.com/vercel/next.js/commit/ff12a6124e1504f17b62de948b8a553fdecaef7b"},{"url":"https://github.com/vercel/next.js/releases/tag/v15.5.21"},{"url":"https://github.com/vercel/next.js/releases/tag/v16.2.11"},{"url":"https://github.com/advisories/GHSA-955p-x3mx-jcvp"}],"tags":["ghsa","npm"],"ingestedAt":"2026-07-22T23:07:32.263Z","epss":0.00516,"epssPercentile":0.42791,"slug":"CVE-2026-64643","body":"## Overview\n\n## Impact\n\nIn Next.js applications using App Router, Server Actions (`use server`) or `use cache` endpoints can be disclosed bypassing any authentication on the pages where these endpoints are usually used.\n\nServer Action IDs can be disclosed to unauthenticated users via publicly served client artifacts (for example, static chunks containing action references).\n\nAffected users are applications using App Router + Server Actions.  \n\nBy itself, this disclosure is typically a recon/enumeration primitive; however, it can increase risk when combined with other weaknesses.\n \n## Workarounds\n\nNever assume any authentication claims at the `use cache` or `use server` boundary. Always authenticate within the boundary.\n\n## Affected packages\n\n- `next >= 13.0.0, < 15.5.21`\n- `next >= 16.0.0, < 16.2.11`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `next 15.5.21`\n- `next 16.2.11`","depth":"sunlit","depthScore":28,"depthScoreParts":{"impact":27.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}