CVE-2026-34944CWE-248

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

Medium · published April 9, 2026

CVSS v4.0
4.1
EPSS
0%
Percentile
16.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
4.1 · MEDIUM
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
EPSS
0.00255 · 16.1th percentile
Weakness
CWE-248 · Uncaught Exception
Published
2026-04-09T18:38Z
EPSS history
Timeline
  • 09 APR 18:38Z
    Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
    cvelistv5