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EUVD-2026-355510

2026-10-06T15:35:12.236434+00:00

EUVD-2026-355510

fkie_cve-2026-52792

2026-10-06T15:35:12.236474+00:00

Algernon is a small self-contained pure-Go web server. Prior to 1.17.9, Algernon on Windows selects a file handler in engine/handlers.go by calling filepath.Ext() without first rejecting NTFS-equivalent names such as x.lua::$DATA, x.lua., and x.lua . An unauthenticated client can append one of these suffixes to a public server-side script using the .lua, .tl, .po2, .amber, or .frm extension. The request path passes through URL2filename in utils/files.go, skips the renderer and execution cases, and reaches FilePage, os.Open, ReadAndLogErrors, and ToClient, while NTFS resolves the alias to the underlying script. The server consequently returns raw script source and can expose database credentials, API keys, and the SetCookieSecret value, which may permit forged session cookies. Linux and macOS hosts are not affected by this issue. This issue is fixed in version 1.17.9.

GHSA-mm6c-5j6x-hq8m — Algernon vulnerable to server-side script source disclosure on Windows via NTFS filename

2026-10-06T15:35:12.236511+00:00

Affected: Go: github.com/xyproto/algernon

### Summary

Algernon selects its file handler from `filepath.Ext()` (engine/handlers.go:134), which does not treat the NTFS-equivalent names `x.lua::$DATA`, `x.lua.`, or `x.lua ` as `.lua`. On Windows, an unauthenticated client appends one of these suffixes to any server-side script on a public path and receives its raw source instead of executed output, leaking embedded secrets such as database credentials and the `SetCookieSecret` value.

Linux and macOS hosts are unaffected.

### Preconditions

- Algernon runs on a Windows host (NTFS filesystem). - The instance serves at least one server-side script (`.lua`, `.tl`, `.po2`, `.amber`, `.frm`). - The script sits on a public path, or no auth backend is configured (`--nodb`, `--simple`, or default no-DB). - HTTP/HTTPS reachability to the server.

### Details

```go // engine/handlers.go:133 lowercaseFilename := strings.ToLower(filename) ext := filepath.Ext(lowercaseFilename) // "index.lua::$data" -> ".lua::$data", not ".lua" [offending] ... if ac.dispatchRenderer(w, req, filename, ext) { // ext unrecognised, returns false return } switch ext { case ".lua", ".tl": // execute the script -- never reached for the equivalent forms // ... RunLua ... default: // control reaches the raw-file branch below } ```

```go // engine/handlers.go:452 f, err := os.Open(filename) // NTFS resolves "index.lua::$DATA" to index.lua's data stream ... // engine/handlers.go:479 if dataBlock, err := ac.ReadAndLogErrors(w, filename, ext);…