CVE-2026-24116CWE-125

Wasmtime segfault or unused out-of-sandbox load with f64.copysign operator on x86-64

Medium · published January 27, 2026

CVSS v4.0
4.1
EPSS
0%
Percentile
15.3
In the wild
Unconfirmed
What it is

Wasmtime is a runtime for WebAssembly. Starting in version 29.0.0 and prior to version 36.0.5, 40.0.3, and 41.0.1, on x86-64 platforms with AVX, Wasmtime's compilation of the `f64.copysign` 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 unless there is another bug in Cranelift this data is not visible to WebAssembly guests. Wasmtime 36.0.5, 40.0.3, and 41.0.1 have been released to fix this issue. Users are recommended to upgrade to the patched versions of Wasmtime. Other affected versions are not patched and users should updated to supported major version instead. This bug can be worked around by enabling signals-based-traps. While disabling guard pages can be a quick fix in some situations, it's not recommended to disabled guard pages as it is a key defense-in-depth measure of Wasmtime.

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
0.00249 · 15.3th percentile
Weakness
CWE-125 · Out-of-bounds Read
Published
2026-01-27T18:58Z
EPSS history
Timeline
  • 27 JAN 18:58Z
    Wasmtime segfault or unused out-of-sandbox load with f64.copysign operator on x86-64
    cvelistv5