{"id":"CVE-2026-25766","aliases":["GHSA-pgvm-wxw2-hrv9","GO-2026-4502"],"url":"https://o3.security/vulnerability/CVE-2026-25766","summary":"Echo has a Windows path traversal via backslash in middleware.Static default filesystem","details":"Echo is a Go web framework. In versions 5.0.0 through 5.0.2 on Windows, Echo’s `middleware.Static` using the default filesystem allows path traversal via backslashes, enabling unauthenticated remote file read outside the static root. In `middleware/static.go`, the requested path is unescaped and normalized with `path.Clean` (URL semantics). `path.Clean` does not treat `\\` as a path separator, so `..\\` sequences remain in the cleaned path. The resulting path is then passed to `currentFS.Open(...)`. When the filesystem is left at the default (nil), Echo uses `defaultFS` which calls `os.Open` (`echo.go:792`). On Windows, `os.Open` treats `\\` as a path separator and resolves `..\\`, allowing traversal outside the static root. Version 5.0.3 fixes the issue.","published":"2026-02-19T15:49:02.402Z","modified":"2026-08-07T11:48:52.126328081Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/labstack/echo/v5","fixedVersion":"5.0.3"}],"fix":{"url":"https://github.com/labstack/echo/commit/b1d443086ea27cf51345ec72a71e9b7e9d9ce5f1","label":"labstack/echo@b1d4430"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/25xxx/CVE-2026-25766.json"},{"type":"ADVISORY","url":"https://github.com/labstack/echo/security/advisories/GHSA-pgvm-wxw2-hrv9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-25766"},{"type":"FIX","url":"https://github.com/labstack/echo/commit/b1d443086ea27cf51345ec72a71e9b7e9d9ce5f1"},{"type":"FIX","url":"https://github.com/labstack/echo/pull/2891"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:48:52.126328081Z"}}