Don't focus on the specific exploit, it's a general issue:
In order to be useful, your wasm application will likely have to be able to make systems calls, or whatever its equivalent might be on your particular host environment. If you can corrupt internal state, you can control the arguments to these calls. The severity of the issue will depend on what your application is allowed to do: If all it has access to is a some virtual file system, the host will still be safe. But if that virtual file system contains sensitive data, results may nevertheless be catastrophic if, say, it can also request resources over http.
In order to be useful, your wasm application will likely have to be able to make systems calls, or whatever its equivalent might be on your particular host environment. If you can corrupt internal state, you can control the arguments to these calls. The severity of the issue will depend on what your application is allowed to do: If all it has access to is a some virtual file system, the host will still be safe. But if that virtual file system contains sensitive data, results may nevertheless be catastrophic if, say, it can also request resources over http.