Rust · Rust · CVE-2023-30624
**Name of the Vulnerable Software and Affected Versions**
Wasmtime versions prior to 6.0.2
Wasmtime versions prior to 7.0.1
Wasmtime versions prior to 8.0.1
**Description**
Wasmtime's implementation of managing per-instance state contains LLVM-level undefined behavior, which can cause runtime-level issues when compiled with LLVM 16. This undefined behavior is due to the use of `unsafe` code to maintain the runtime state for an instance, which involves a Rust-defined structure called `Instance` with a trailing `VMContext` structure. The code has methods that take `&self` as an argument but modify data in the `VMContext` part of the allocation, which is typically not allowed in Rust.
The estimated number of potentially affected devices worldwide is not available.
There is no information about real-world incidents where this issue was exploited.
Technical details about exploitation include:
- The `VMContext` structure has a runtime-defined layout that is unique per-module.
- The code doing this has methods which take `&self` as an argument but modify data in the `VMContext` part of the allocation.
- This means that pointers derived from `&self` are mutated, which is typically not allowed, except in the presence of `UnsafeCell`, in Rust.
- When compiled to LLVM these functions have `noalias readonly` parameters which means it's undefined behavior to write through the pointers.
**Recommendations**
Update to Wasmtime version 6.0.2 or later if you are using version prior to 6.0.2.
Update to Wasmtime version 7.0.1 or later if you are using version prior to 7.0.1.
Update to Wasmtime version 8.0.1 or later if you are using version prior to 8.0.1.
If Wasmtime is compiled with Rust 1.69 and prior, which use LLVM 15, then there are no known issues, but it's still recommended to update to a patched version of Wasmtime.
Users using beta Rust (1.70 or later) or nightly Rust (1.71 or later) must update to a patched version to work correctly.