Bug 2456998 (CVE-2026-34946)

Summary: CVE-2026-34946 wasmtime: Wasmtime: Denial of Service via WebAssembly compilation error
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
Version: unspecifiedKeywords: Security
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A flaw was found in Wasmtime, a runtime for WebAssembly (Wasm) code. A malicious Wasm program, when processed by Wasmtime's Winch compiler, can cause the underlying system to crash. This is due to an error in how the compiler handles certain instructions, leading to a Denial of Service (DoS) vulnerability where the system becomes unavailable.
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Bug Depends On: 2457169    
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Description OSIDB Bzimport 2026-04-09 19:02:01 UTC 
Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a vulnerability where the compilation of the table.fill instruction can result in a host panic. This means that a valid guest can be compiled with Winch, on any architecture, and cause the host to panic. This represents a denial-of-service vulnerability in Wasmtime due to guests being able to trigger a panic. The specific issue is that a historical refactoring changed how compiled code referenced tables within the table.* instructions. This refactoring forgot to update the Winch code paths associated as well, meaning that Winch was using the wrong indexing scheme. Due to the feature support of Winch the only problem that can result is tables being mixed up or nonexistent tables being used, meaning that the guest is limited to panicking the host (using a nonexistent table), or executing spec-incorrect behavior and modifying the wrong table. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.