AIKIDO-2026-627943

TL;DR

The wasmtime package ships the precompiled Wasmtime runtime, whose WASI filesystem layer enforces per-directory and per-file permissions on preopened directories. When a host preopens a directory with writable directory permissions but read-only file permissions, a guest module can call path_open using only the truncate flag to open and truncate a file that should be read-only, because the truncate path is not treated as a write for the permission check. This lets sandboxed WebAssembly modules destroy or overwrite file contents the embedder intended to expose read-only. The fix marks truncating opens as writes so the file-permission check rejects them.