{"id":"CVE-2025-71399","aliases":["EUVD-2025-210590","GHSA-9fq7-6g6p-g9rm","GHSA-x732-6j76-qmhm"],"status":"published","title":"Better Auth before 1.4.5 Path Normalization Bypass via rou3","description":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.","severity":{"version":"4.0","score":8.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.0052,"percentile":0.44665,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-20","CWE-400","CWE-41"],"published":"2025-12-16T21:22:45Z","modified":"2026-10-28T02:31:00Z","fixes":[{"ecosystem":"npm","package":"better-auth","fixed_in":["1.4.5"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"better-auth","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.4.5"}]}]},{"source":"osv","ecosystem":"npm","package":"better-auth","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.4.5"}]}]}],"products":[{"vendor":"better-auth","product":"better-auth"}],"references":[{"url":"https://github.com/better-auth/better-auth/security/advisories/GHSA-x732-6j76-qmhm","tags":["vendor-advisory","advisory","web"]},{"url":"https://github.com/better-auth/better-auth/commit/f60b43fa648399534507c9ac7db36d705b8874c3","tags":["patch","fix"]},{"url":"https://www.vulncheck.com/advisories/better-auth-before-path-normalization-bypass-via-rou3","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-71399","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-9fq7-6g6p-g9rm"},{"url":"https://github.com/advisories/GHSA-x732-6j76-qmhm"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/71xxx/CVE-2025-71399.json","tags":["advisory"]},{"url":"https://github.com/better-auth/better-auth","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2025-71399","title":"Better Auth before 1.4.5 Path Normalization Bypass via rou3","description":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.","status":"published","published":"2026-08-02T12:15:22.129Z","modified":"2026-10-08T15:21:31.928Z","cvss":[{"version":"4.0","score":8.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N","level":"high","assessor":"cna"},{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:32:42.751171Z"}],"euvd":[{"id":"EUVD-2025-210590","description":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.","status":"published","published":"2026-08-02T12:15:22Z","modified":"2026-10-08T15:21:31Z","cvss":[{"version":"4.0","score":8.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T17:27:32.18003Z"}],"ghsa":[{"id":"GHSA-9fq7-6g6p-g9rm","title":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of...","description":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.","status":"published","published":"2026-08-02T15:30:21Z","modified":"2026-08-02T15:30:21Z","cvss":[{"version":"4.0","score":8.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high"},{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","level":"high"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:10:01.548476Z"},{"id":"GHSA-x732-6j76-qmhm","title":"Better Auth's rou3 Dependency has Double-Slash Path Normalization which can Bypass disabledPaths Config and Rate Limits","description":"## Summary\n\nAn issue in the underlying router library **rou3** can cause `/path` and `//path` to be treated as identical routes. If your environment does **not** normalize incoming URLs (e.g., by collapsing multiple slashes), this can allow bypasses of `disabledPaths` and path-based rate limits.\n\n## Details\n\nBetter Auth uses **better-call**, which internally relies on **rou3** for routing. Affected versions of rou3 normalize paths by removing empty segments. As a result:\n\n* `/sign-in/email`\n* `//sign-in/email`\n* `///sign-in/email`\n\n…all resolve to the same route.\n\nSome production setups *automatically* collapse multiple slashes. This includes:\n\n* Vercel with Nextjs (default)\n* Cloudflare - when normalize to urls origin is enabled (https://developers.cloudflare.com/rules/normalization/settings/#normalize-urls-to-origin)\n\nIn these environments and other configurations where `//path` reach Better Auth as `/path`, the issue does not apply.\n\n## Fix\n\nUpdating rou3 to the latest version resolves the issue:\n\n* better-call previously depended on `\"rou3\": \"^0.5.1\"`\n* The fix was introduced after that version\n  (commit: [https://github.com/h3js/rou3/commit/f60b43fa648399534507c9ac7db36d705b8874c3](https://github.com/h3js/rou3/commit/f60b43fa648399534507c9ac7db36d705b8874c3))\n\nBetter Auth recommends:\n\n1. **Upgrading to Better Auth v1.4.5 or later**, which includes the updated rou3.\n2. Ensuring the proxy normalizes URLs.\n3. If project maintainers cannot upgrade yet, they can protect their app by normalizing url before it reaches better-auth handler. See example below:\n```ts\nconst req = new Request(...) // this would be the actual request object\nconst url = new URL(req.url);\nconst normalizedPath = url.pathname.replace(/\\/+/g, \"/\");\n\nif (url.pathname !== normalizedPath) {\n  url.pathname = normalizedPath;\n  // Update the raw request pathname\n  Object.defineProperty(req, \"url\", {\n    value: url.toString(),\n    writable: true,\n    configurable: true,\n  });\n}\n```\n\n## Impact\n\n* Bypass `disabledPaths`\n* Bypass path-based rate limits\n\nThe impact of bypassing disabled paths could vary based on a project's configuration.","status":"published","published":"2025-12-16T21:22:45Z","modified":"2025-12-16T21:22:47Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","level":"high"}],"cwes":["CWE-41","CWE-400"],"updated_at":"2026-11-02T14:39:13.204325Z"}],"nvd":[{"id":"CVE-2025-71399","description":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.","status":"published","published":"2026-08-02T13:16:52.21Z","modified":"2026-10-08T16:16:53.243Z","cvss":[{"version":"4.0","score":8.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"high","assessor":"secondary"},{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:12:03.20248Z"}],"osv":[{"id":"CVE-2025-71399","title":"Better Auth before 1.4.5 Path Normalization Bypass via rou3","description":"Better Auth relies on better-call, which uses the rou3 router library. In affected versions of rou3, paths are normalized by removing empty segments, so /path, //path, and ///path resolve to the same route. In Better Auth versions prior to 1.4.5 (which bundles the fixed rou3), this can allow attackers to bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply in deployments where the proxy or platform normalizes URLs by collapsing multiple slashes.","status":"published","published":"2026-08-02T12:15:22.129Z","modified":"2026-10-28T02:31:00.122005634Z","cvss":[{"version":"4.0","score":8.8,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T15:44:53.185592Z"},{"id":"GHSA-x732-6j76-qmhm","title":"Better Auth's rou3 Dependency has Double-Slash Path Normalization which can Bypass disabledPaths Config and Rate Limits","description":"## Summary\n\nAn issue in the underlying router library **rou3** can cause `/path` and `//path` to be treated as identical routes. If your environment does **not** normalize incoming URLs (e.g., by collapsing multiple slashes), this can allow bypasses of `disabledPaths` and path-based rate limits.\n\n## Details\n\nBetter Auth uses **better-call**, which internally relies on **rou3** for routing. Affected versions of rou3 normalize paths by removing empty segments. As a result:\n\n* `/sign-in/email`\n* `//sign-in/email`\n* `///sign-in/email`\n\n…all resolve to the same route.\n\nSome production setups *automatically* collapse multiple slashes. This includes:\n\n* Vercel with Nextjs (default)\n* Cloudflare - when normalize to urls origin is enabled (https://developers.cloudflare.com/rules/normalization/settings/#normalize-urls-to-origin)\n\nIn these environments and other configurations where `//path` reach Better Auth as `/path`, the issue does not apply.\n\n## Fix\n\nUpdating rou3 to the latest version resolves the issue:\n\n* better-call previously depended on `\"rou3\": \"^0.5.1\"`\n* The fix was introduced after that version\n  (commit: [https://github.com/h3js/rou3/commit/f60b43fa648399534507c9ac7db36d705b8874c3](https://github.com/h3js/rou3/commit/f60b43fa648399534507c9ac7db36d705b8874c3))\n\nBetter Auth recommends:\n\n1. **Upgrading to Better Auth v1.4.5 or later**, which includes the updated rou3.\n2. Ensuring the proxy normalizes URLs.\n3. If project maintainers cannot upgrade yet, they can protect their app by normalizing url before it reaches better-auth handler. See example below:\n```ts\nconst req = new Request(...) // this would be the actual request object\nconst url = new URL(req.url);\nconst normalizedPath = url.pathname.replace(/\\/+/g, \"/\");\n\nif (url.pathname !== normalizedPath) {\n  url.pathname = normalizedPath;\n  // Update the raw request pathname\n  Object.defineProperty(req, \"url\", {\n    value: url.toString(),\n    writable: true,\n    configurable: true,\n  });\n}\n```\n\n## Impact\n\n* Bypass `disabledPaths`\n* Bypass path-based rate limits\n\nThe impact of bypassing disabled paths could vary based on a project's configuration.","status":"published","published":"2025-12-16T21:22:45Z","modified":"2026-08-03T03:41:44.584235266Z","cvss":[{"version":"3.1","score":8.6,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H","level":"high"}],"cwes":["CWE-400","CWE-41"],"updated_at":"2026-11-02T15:46:59.484835Z"}]}}