| Summary | Werkzeug safe_join() allows Windows special device names with compound extensions
Werkzeug's `safe_join` function allows path segments with Windows device names that have file extensions or trailing spaces. On Windows, there are special device names such as `CON`, `AUX`, etc that are implicitly present and readable in every directory. Windows still accepts them with any file extension, such as `CON.txt`, or trailing spaces such as `CON `.
This was previously reported as https://github.com/pallets/werkzeug/security/advisories/GHSA-hgf8-39gv-g3f2, but the fix failed to account for compound extensions such as `CON.txt.html` or trailing spaces. It also missed some additional special names.
`send_from_directory` uses `safe_join` to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely. |
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