Bug 2457005 (CVE-2026-34943)

Summary: CVE-2026-34943 Wasmtime: Wasmtime: Denial of Service due to malformed flags-typed component model value processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Wasmtime, a runtime for WebAssembly. A malicious guest can exploit an issue where a flags-typed component model value, containing unexpected bit settings, causes the host system to panic during processing. This vulnerability can lead to a Denial of Service (DoS), rendering the host system unresponsive.
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Bug Depends On: 2457174    
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Description OSIDB Bzimport 2026-04-09 19:02:37 UTC 
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.