CVE-2022-31104

What it is

Wasmtime is a standalone runtime for WebAssembly. In affected versions wasmtime's implementation of the SIMD proposal for WebAssembly on x86_64 contained two distinct bugs in the instruction lowerings implemented in Cranelift. The aarch64 implementation of the simd proposal is not affected. The bugs were presented in the `i8x16.swizzle` and `select` WebAssembly instructions. The `select` instruction is only affected when the inputs are of `v128` type. The correspondingly affected Cranelift instructions were `swizzle` and `select`. The `swizzle` instruction lowering in Cranelift erroneously overwrote the mask input register which could corrupt a constant value, for example. This means that future uses of the same constant may see a different value than the constant itself. The `select` instruction lowering in Cranelift wasn't correctly implemented for vector types that are 128-bits wide. When the condition was 0 the wrong instruction was used to move the correct input to the output of the instruction meaning that only the low 32 bits were moved and the upper 96 bits of the result were left as whatever the register previously contained (instead of the input being moved from). The `select` instruction worked correctly if the condition was nonzero, however. This bug in Wasmtime's implementation of these instructions on x86_64 represents an incorrect implementation of the specified semantics of these instructions according to the WebAssembly specification. The impact of this is benign for hosts running WebAssembly but represents possible vulnerabilities within the execution of a guest program. For example a WebAssembly program could take unintended branches or materialize incorrect values internally which runs the risk of exposing the program itself to other related vulnerabilities which can occur from miscompilations. We have released Wasmtime 0.38.1 and cranelift-codegen (and other associated cranelift crates) 0.85.1 which contain the corrected implementations of these two instructions in Cranelift. If upgrading is not an option for you at this time, you can avoid the vulnerability by disabling the Wasm simd proposal. Additionally the bug is only present on x86_64 hosts. Other aarch64 hosts are not affected. Note that s390x hosts don't yet implement the simd proposal and are not affected.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

1.8% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2022-06-28 00:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:44 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.8% in the next 30 days (EPSS).
• Severity: 4.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2022-06-28 00:15 UTC

Last modified

2026-06-17 04:44 UTC

Exploit probability

1.8% · EPSS, next 30 days

Weakness

CWE-682

Record status

Modified

Affected

• Bytecodealliance cranelift-codegen < 0.85.0
• Bytecodealliance Wasmtime < 0.38.1

Attack profile CVSS 3.1 · 4.8

Attack vector

Network

Complexity

High

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2022-31104.md and follow it. Check whether this project is affected by CVE-2022-31104. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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