CVE-2026-34944 MEDIUM

CVE-2026-34944: Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64

Vendor Bytecodealliance
Product wasmtime
Weakness CWE-248
Published April 9, 2026
Last update April 13, 2026

CVSS base score

4.1/10
Attack vector Local
Attack complexity Low
Privileges required Low
User interaction
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

What the vulnerability does

01Description

Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, On x86-64 platforms with SSE3 disabled Wasmtime's compilation of the f64x2.splat WebAssembly instruction with Cranelift may load 8 more bytes than is necessary. When signals-based-traps are disabled this can result in a uncaught segfault due to loading from unmapped guard pages. With guard pages disabled it's possible for out-of-sandbox data to be loaded, but this data is not visible to WebAssembly guests. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.

Key dates

02Disclosure timeline

April 9, 2026 CVE published
April 13, 2026 Record updated