{"id":"GO-2026-4950","aliases":[],"status":"published","title":"Authorization bypass via double-encoded paths in github.com/valyala/fasthttp","description":"In github.com/valyala/fasthttp before 1.70.0, ServeFile and ServeFS reinterpret filesystem paths as URIs, decoding percent-encoded sequences and treating characters like '?' and '#' as URI delimiters. In applications where authorization guards inspect ctx.Path() before passing paths to file-serving handlers, double-encoded path variants (e.g., /%2561dmin/export.csv) bypass access controls while still resolving to the protected file on disk.","facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"published":"2026-08-18T18:05:09Z","modified":"2026-08-19T15:41:58Z","fixes":[{"ecosystem":"Go","package":"github.com/valyala/fasthttp","fixed_in":["1.70.0"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Go","package":"github.com/valyala/fasthttp","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.70.0"}]}]}],"references":[{"url":"https://github.com/golang/vulndb/issues/4950","tags":["report"]},{"url":"https://github.com/valyala/fasthttp/pull/2163","tags":["fix"]},{"url":"https://gist.github.com/thesmartshadow/af53acdfe0d6ce352d14eb86cecf5a08","tags":["web"]},{"url":"https://github.com/valyala/fasthttp/releases/tag/v1.70.0","tags":["web"]}],"sources":{"osv":[{"id":"GO-2026-4950","title":"Authorization bypass via double-encoded paths in github.com/valyala/fasthttp","description":"In github.com/valyala/fasthttp before 1.70.0, ServeFile and ServeFS reinterpret filesystem paths as URIs, decoding percent-encoded sequences and treating characters like '?' and '#' as URI delimiters. In applications where authorization guards inspect ctx.Path() before passing paths to file-serving handlers, double-encoded path variants (e.g., /%2561dmin/export.csv) bypass access controls while still resolving to the protected file on disk.","status":"published","published":"2026-08-18T18:05:09Z","modified":"2026-08-19T15:41:58.201679153Z","updated_at":"2026-11-02T15:47:02.280725Z"}]}}