{"id":"GHSA-hq75-xg7r-rx6c","summary":"Better Call routing bug can lead to Cache Deception","details":"### Summary\n\nUsing a CDN that caches (`/**/*.png`, `/**/*.json`, `/**/*.css`, etc...) requests, a cache deception can emerge. This could lead to unauthorized access to user sessions and personal data when cached responses are served to other users.\n\n### Details\n\nThe vulnerability occurs in the request processing logic where path sanitization is insufficient. The library splits the path using `config.basePath` but doesn't properly validate the remaining path components. This allows specially crafted requests that appear to be static assets (like `/api/auth/get-session/api/auth/image.png` assuming `config.basePath`=`/api/auth`) to bypass typical CDN cache exclusion rules while actually returning sensitive data.\n\nThe problematic code [here](https://github.com/Bekacru/better-call/blob/8b6f13e24fad7f4666a582601517bb3232d4f4af/src/router.ts#L124):\n```js\n\tconst processRequest = async (request: Request) =\u003e {\n\t\tconst url = new URL(request.url);\n\t\tconst path = config?.basePath ? url.pathname.split(config.basePath)[1] : url.pathname;\n```\n\nSince this library is largely coupled with `better-auth`, it becomes more clear why this can be dangerous with an example request:\n\n\u003cimg width=\"800\" alt=\"image\" src=\"https://github.com/user-attachments/assets/2ab7c4dd-0700-4f59-863f-79f2b5edbb37\" /\u003e\n\n### Impact\n\nThis is a cache deception vulnerability affecting `better-call` users with CDN caching enabled. which can expose sensitive data.","modified":"2025-07-11T17:09:53Z","published":"2025-07-11T17:09:53Z","database_specific":{"cwe_ids":["CWE-525"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2025-07-11T17:09:53Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/Bekacru/better-call/security/advisories/GHSA-hq75-xg7r-rx6c"},{"type":"WEB","url":"https://github.com/Bekacru/better-call/commit/7c7d31b"},{"type":"PACKAGE","url":"https://github.com/Bekacru/better-call"}],"affected":[{"package":{"name":"better-call","ecosystem":"npm","purl":"pkg:npm/better-call"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.0.12"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2025/07/GHSA-hq75-xg7r-rx6c/GHSA-hq75-xg7r-rx6c.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U"}]}