CVE-2026-54913

WebAssembly Micro Runtime (WAMR) is a lightweight standalone WebAssembly (Wasm) runtime. Prior to 2.4.5, load init expr in core/iwasm/interpreter/wasm loader.c accepts a non-reference heap-type byte for ref.null when WASM ENABLE GC=0, while the local WASMValue cur value union is not zero-initialized and setting ref index writes only part of it. A crafted module can declare an i64, f64, or v128 global initialized through the invalid ref.null form, causing push const expr stack and the later global initialization path to copy uninitialized host-stack bytes into a value readable by the guest. The classic and fast interpreters are affected in the default no-GC configuration; the GC-enabled path validates heap types. The disclosure is four bytes for i64 or f64 globals and up to twelve bytes for each v128 global. This issue is fixed in version 2.4.5.