The underlying problem is that Wasmtime's runtime state for an instance involves a Rust-defined structure called `Instance` which has a trailing `VMContext` structure after it. This `VMContext` structure has a runtime-defined layout that is unique per-module. This representation cannot be expressed with safe code in Rust so `unsafe` code is required to maintain this state. The code doing this, however, 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. This 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 UB to write through the pointers.
Wasmtime's internal representation and management of `VMContext` has been updated to use `&mut self` methods where appropriate. Additionally verification tools for `unsafe` code in Rust, such as `cargo miri`, are planned to be executed on the `main` branch soon to fix any Rust-level issues that may be exploited in future compiler versions.
Precomplied binaries available for Wasmtime from GitHub releases have been compiled with at most LLVM 15 so are not known to be vulnerable. As mentioned above, however, it's still recommended to update.
Wasmtime version 6.0.2, 7.0.1, and 8.0.1 have been issued which contain the patch necessary to work correctly on LLVM 16 and have no known UB on LLVM 15 and earlier. If Wasmtime is compiled with Rust 1.69 and prior, which use LLVM 15, then there are no known issues. There is a theoretical possibility for undefined behavior to exploited, however, so it's recommended that users upgrade to a patched version of Wasmtime. Users using beta Rust (1.70 at this time) or nightly Rust (1.71 at this time) must update to a patched version to work correctly.
Analysis and contextual insights are available on OpenCVE Cloud.
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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| Source | ID | Title |
|---|---|---|
EUVD |
EUVD-2023-1270 | Undefined Behavior in Rust runtime functions |
Github GHSA |
GHSA-ch89-5g45-qwc7 | Undefined Behavior in Rust runtime functions |
Thu, 30 Jan 2025 20:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2025-01-30T19:33:32.271Z
Reserved: 2023-04-13T13:25:18.833Z
Link: CVE-2023-30624
Updated: 2024-08-02T14:28:52.059Z
Status : Modified
Published: 2023-04-27T17:15:08.737
Modified: 2024-11-21T08:00:32.103
Link: CVE-2023-30624
No data.
OpenCVE Enrichment
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EUVD
Github GHSA