CVE-2023-27477 : Vulnerability Insights and Analysis

This CVE was published on March 8, 2023, by GitHub_M regarding a vulnerability in the wasmtime runtime for WebAssembly, specifically affecting the Cranelift code generation backend on x86_64 platforms.

Understanding CVE-2023-27477

The vulnerability in this CVE pertains to a bug in the WebAssembly

i8x16.select

instruction within Wasmtime's code generation backend, Cranelift. This bug results in incorrect results when the same operand is provided to the instruction and selected indices are greater than 16.

What is CVE-2023-27477?

The CVE-2023-27477 vulnerability in Wasmtime's Cranelift code generation backend affects x86_64 platforms due to an off-by-one error in the calculation of the mask to the

pshufb

instruction, leading to incorrect results when lanes are selected from the second vector.

The Impact of CVE-2023-27477

This vulnerability can potentially result in miscompilations when using the affected versions of Wasmtime on x86_64 hosts. Other platforms such as AArch64 and s390x are not impacted by this bug.

Technical Details of CVE-2023-27477

The vulnerability is present in Wasmtime versions 4.0.1, 5.0.1, and 6.0.1, specifically affecting certain versions of the Cranelift codegen component.

Vulnerability Description

The bug in the Cranelift code generation backend causes incorrect results when processing the

i8x16.select

instruction due to the off-by-one error in mask calculation.

Affected Systems and Versions

Versions of Wasmtime and Cranelift codegen ranging from cranelift-codegen: >= 0.88.0 to < 0.91.1, 0.92.0 to < 0.92.1, and 0.93.0 to < 0.93.1, as well as wasmtime: >= 0.37.0 to < 4.0.1, 5.0.0 to < 5.0.1, and 6.0.0 to < 6.0.1 are vulnerable to this bug.

Exploitation Mechanism

The bug manifests in the incorrect processing of the

i8x16.select

instruction in WebAssembly, leading to unexpected output when provided with certain operands and selected indices.

Mitigation and Prevention

To address CVE-2023-27477 and mitigate its impact, users are advised to take immediate action and follow recommended security practices.

Immediate Steps to Take

Upgrade to the fixed versions of Wasmtime (6.0.1, 5.0.1, and 4.0.1) to prevent miscompilations caused by the bug. If immediate upgrading is not possible, consider disabling the Wasm SIMD proposal to avoid encountering this vulnerability.

Long-Term Security Practices

In the long term, it is crucial to stay updated with security advisories from relevant sources such as bytechodealliance and promptly apply patches and updates to prevent potential exploitation of vulnerabilities.

Patching and Updates

Regularly check for security advisories and updates from Wasmtime and Cranelift to ensure that your runtime environment is protected against known security vulnerabilities.