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

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
bytecodealliance / wasmtime	affected < 24.0.7; affected >= 25.0.0, < 36.0.7; affected >= 37.0.0, < 42.0.2; affected >= 43.0.0, < 44.0.1

CWE

CWE-248

References

https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-qqfj-4vcm-26hv

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.