CVE-2026-47261
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk41th percentile - higher than 41% of all known CVEs
Summary
Wasmtime, a runtime for WebAssembly, has a vulnerability in versions prior to 24.0.9, 36.0.10, and 44.0.2 that allows bypassing the access control mechanism using the wasip2 descriptor.open-at or wasip1 path_open interfaces. The issue arises from a missing assignment in the open mode handling, allowing files to be opened with the OpenFlags::TRUNCATE flag without the necessary write permissions.
Risk Assessment
Organizations may be exposed to unauthorized file access, potentially leading to data leaks or unauthorized modifications. This affects only wasmtime-wasi embeddings that combine DirPerms::MUTATE with FilePerms::READ.
Recommendation
It is recommended to upgrade to versions 24.0.9, 36.0.10, or 44.0.2 to mitigate this vulnerability. Additionally, review the permission configurations in wasmtime-wasi embeddings.
Original NVD description (English source)
Wasmtime is a runtime for WebAssembly. In versions prior to 24.0.9, 36.0.10, and 44.0.2, when a filesystem preopen is given DirPerms::all() and FilePerms::READ without FilePerms::WRITE, this access control mechanism can be bypassed via the wasip2 descriptor.open-at or wasip1 path_open interfaces by opening a file with only the OpenFlags::TRUNCATE oflag. The root cause is that the clause handling OpenFlags::TRUNCATE in crates/wasi/src/filesystem.rs (Dir::open_at, lines 967–969) did not set open_mode |= OpenMode::WRITE;, which is later used for the access control check against FilePerms to determine whether opening the file is permitted; the single-line fix adds that missing assignment, after which the affected calls correctly fail with error-code.not-permitted and ERRNO_PERM respectively. Only wasmtime-wasi embeddings that combine DirPerms::MUTATE with FilePerms::READ are affected by this bug. In particular, the Wasmtime project's wasmtime-cli's use of wasmtime-wasi is not affected, because it always sets FilePerms::all() for all preopens. This issue has been fixed in versions 24.0.9, 36.0.10 and44.0.2.