CVE-2022-31104 : Exploit Details and Defense Strategies

Wasmtime, a standalone runtime for WebAssembly, was found to have a miscompilation issue in the

i8x16.swizzle

and

select

instructions with

v128

inputs. This vulnerability impacts certain versions of Wasmtime and cranelift-codegen, leading to possible vulnerabilities within the execution of a guest program.

Understanding CVE-2022-31104

This CVE discloses a miscompilation issue in the

i8x16.swizzle

and

select

instructions in Wasmtime, affecting specific versions.

What is CVE-2022-31104?

In affected versions, Wasmtime's implementation of the SIMD proposal for WebAssembly on x86_64 contained bugs in the instruction lowerings implemented in Cranelift. The bugs were specifically in the

i8x16.swizzle

and

select

WebAssembly instructions.

The Impact of CVE-2022-31104

The miscompilation could result in unintended branches or materialize incorrect values internally, posing risks of exposing the program to vulnerabilities from miscompilations.

Technical Details of CVE-2022-31104

This section delves into the specifics of the vulnerability.

Vulnerability Description

The bug in Wasmtime's implementation of the instructions on x86_64 represents an incorrect implementation of the specified semantics according to the WebAssembly specification.

Affected Systems and Versions

The vulnerability affects

wasmtime: < 0.38.1

and

cranelift-codegen: < 0.85.0

.

Exploitation Mechanism

The miscompilation occurs in the handling of the

i8x16.swizzle

and

select

instructions with

v128

inputs.

Mitigation and Prevention

It's crucial to take immediate steps to secure systems and prevent potential exploitation.

Immediate Steps to Take

Upgrade to Wasmtime 0.38.1 and cranelift-codegen 0.85.1 to address the miscompilation issues.

Long-Term Security Practices

Consider disabling the Wasm SIMD proposal if immediate upgrading is not feasible to mitigate the vulnerability.

Patching and Updates

Regularly update Wasmtime and associated cranelift crates to stay protected from known vulnerabilities.