Description
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.
Published: 2026-11-05
Score: 6.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Thu, 05 Nov 2026 17:45:00 +0000

Type Values Removed Values Added
Description 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.
Title WebAssembly Micro Runtime: Missing `ref.null` heap-type validation in `load_init_expr` leaks host stack memory to the WebAssembly guest
Weaknesses CWE-457
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N'}

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-11-05T17:28:26.923Z

Reserved: 2026-06-16T13:49:33.556Z

Link: CVE-2026-54913

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-05T18:17:08.703

Modified: 2026-11-05T18:17:08.703

Link: CVE-2026-54913

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses
  • CWE-457

    Use of Uninitialized Variable