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EUVD-2026-292408

fkie_cve-2026-40876

goshs is a SimpleHTTPServer written in Go. Prior to 2.0.0-beta.6, goshs contains an SFTP root escape caused by prefix-based path validation. An authenticated SFTP user can read from and write to filesystem paths outside the configured SFTP root, which breaks the intended jail boundary and can expose or modify unrelated server files. The SFTP subsystem routes requests through sftpserver/sftpserver.go into DefaultHandler.GetHandler() in sftpserver/handler.go, which forwards file operations into readFile, writeFile, listFile, and cmdFile. All of those sinks rely on sanitizePath() in sftpserver/helper.go. helper.go uses a raw string-prefix comparison, not a directory-boundary check. Because of that, if the configured root is /tmp/goshsroot, then a sibling path such as /tmp/goshsroot_evil/secret.txt incorrectly passes validation since it starts with the same byte prefix. This vulnerability is fixed in 2.0.0-beta.6.

GHSA-5h6h-7rc9-3824 — SFTP root escape via prefix-based path validation in goshs

Affected: Go: github.com/patrickhener/goshs, Go: github.com/patrickhener/goshs/v2

### Summary goshs contains an SFTP root escape caused by prefix-based path validation. An authenticated SFTP user can read from and write to filesystem paths outside the configured SFTP root, which breaks the intended jail boundary and can expose or modify unrelated server files.

### Details The SFTP subsystem routes requests through `sftpserver/sftpserver.go:99-126` into `DefaultHandler.GetHandler()` in `sftpserver/handler.go:90-112`, which forwards file operations into `readFile`, `writeFile`, `listFile`, and `cmdFile`. All of those sinks rely on `sanitizePath()` in `sftpserver/helper.go:47-59`. The vulnerable logic is:

```go cleanPath = filepath.Clean("/" + clientPath) if !strings.HasPrefix(cleanPath, sftpRoot) { return "", errors.New("access denied: outside of webroot") } ```

This is a raw string-prefix comparison, not a directory-boundary check. Because of that, if the configured root is `/tmp/goshsroot`, then a sibling path such as `/tmp/goshsroot_evil/secret.txt` incorrectly passes validation since it starts with the same byte prefix.

That unsafe value then reaches filesystem sinks including:

- `os.Open` in `sftpserver/helper.go:80-94` - `os.Create` in `sftpserver/helper.go:139-152` - `os.Rename` in `sftpserver/helper.go:214-221` - `os.RemoveAll` in `sftpserver/helper.go:231-232` - `os.Mkdir` in `sftpserver/helper.go:242-243`

This means an authenticated SFTP user can escape the configured jail and read, create, upload, rename, or delete content outside the i…