What’s Vulnerable › Vulnerabilities
CVE-2026-34944: Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
- Severity: medium (CVSS 5.7 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-09 · updated 2026-10-26
- Weakness: CWE-248
Description
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 products
- bytecodealliance wasmtime: before 24.0.7; from 25.0.0 before 36.0.7; from 37.0.0 before 42.0.2; from 43.0.0 before 43.0.1 — fixed in 24.0.7, 36.0.7, 42.0.2, 43.0.1
How to fix
Upgrade to a fixed version: bytecodealliance wasmtime 24.0.7, 36.0.7, 42.0.2, 43.0.1. Check the vendor advisory for mitigations.
References
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