EUVD-2026-21023
GHSA-qqfj-4vcm-26hv
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
4Description
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.
Analysis
Wasmtime's Cranelift compiler generates inefficient code for the f64x2.splat WebAssembly instruction on x86-64 platforms with SSE3 disabled, causing it to load 8 excess bytes beyond the intended operand. On systems with signals-based traps disabled, this overflow access can trigger segmentation faults from unmapped guard pages; with guard pages also disabled, out-of-sandbox memory is accessible to the runtime (though not to WebAssembly guests themselves). …
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External POC / Exploit Code
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