Two Critical Wasmtime Flaws Could Let Malicious WebAssembly Modules Escape Sandboxes
Two critical flaws in Wasmtime , a WebAssembly runtime that can be built into other software, could allow a malicious WebAssembly module to escape the sandbox intended to contain it, the project's maintainers say. An attacker would first need a vulnerable Wasmtime build to compile a module they control, and one of the flaws affects only ARM64 systems. Fixed versions were released on October 19 and 20, and the maintainers have not reported any attacks. Wasmtime runs WebAssembly code outside web browsers. Both bugs are in Cranelift, the compiler it uses by default to turn WebAssembly into machine code. Wasmtime's maintainers at the Bytecode Alliance rated each flaw 9.9 out of 10 on the CVSS scale in advisories published on October 19. CVE-2026-115889 affects Wasmtime across all processor architectures. CVE-2026-115893 affects only ARM64, also called aarch64. The sandbox is meant to keep a module inside set limits. A module can only use its own memory and...
Oct 26, 2026