Wasmtime out of bounds read/write with zero-memory-pages configuration
Date: 2022-11
Affected: rust/wasmtime, rust/wasmtime
Attack vector: other
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2022-39392
CWE: CWE-119
CWE-125
CWE-787
CVSS: 5.9 (CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N)

### Impact There is a bug in Wasmtime's implementation of its pooling instance allocator when the allocator is configured to give WebAssembly instances a maximum of zero pages of memory. In this configuration the virtual memory mapping for WebAssembly memories did not meet the compiler-required configuration requirements for safely executing WebAssembly modules. Wasmtime's default settings require virtual memory page faults to indicate that wasm reads/writes are out-of-bounds, but the pooling allocator's configuration would not create an appropriate virtual memory mapping for this meaning out of bounds reads/writes can successfully read/write memory unrelated to the wasm sandbox within range of the base address of the memory mapping created by the pooling allocator. This bug can only be triggered by setting [`InstanceLimits::memory_pages`](https://docs.rs/wasmtime/2.0.1/wasmtime/struct.InstanceLimits.html#structfield.memory_pages) to zero. This is expected to be a very rare configuration since this means that wasm modules cannot allocate any pages of linear memory. All wasm modules produced by all current toolchains are highly likely to use linear memory, so it's expected to be unlikely that this configuration is set to zero by any production embedding of Wasmtime, hence the low severity of this bug despite the critical consequences. ### Patches This bug has been patched and users should upgrade to Wasmtime 2.0.2. ### Workarounds One way to mitigate this issue is to dis


Mitigations:

Architectural layers (MAESTRO):