Shumbo

**Name of the Vulnerable Software and Affected Versions** wasmtime-wasi (affected versions not specified) **Description** An access control mechanism bypass exists when a filesystem preopen is configured with `DirPerms::all()` and `FilePerms::READ` without `FilePerms::WRITE`. This allows bypassing restrictions by using the wasip2 `descriptor.open-at` or wasip1 `path open` interfaces to open a file using only the `OpenFlags::TRUNCATE` flag. The issue stems from the `Dir::open at()` function in `crates/wasi/src/filesystem.rs`, where the logic handling `OpenFlags::TRUNCATE` fails to set the `open mode` to `OpenMode::WRITE`, which is required for the subsequent access control check against `FilePerms`. **Recommendations** At the moment, there is no information about a newer version that contains a fix for this vulnerability.