Wasmtime panics when lifting `flags` component value
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-34943
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 7 Nov 2026, 04:54 UTC · Revision 1
Source evidence
Wasmtime panics when lifting `flags` component value
core-osv · Original sourcePublished 9 Apr 2026, 18:36 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.
osv:CVE-2026-34943
Complete source record
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"id": "9f573542baea188a1eb3e434870939b6c6723652873f19d4efa042e7a951b505",
"url": "https://osv.dev/vulnerability/CVE-2026-34943",
"method": "structured",
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"title": "Wasmtime panics when lifting `flags` component value",
"summary": "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.",
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"RUSTSEC-2026-0085"
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"modified": "2026-10-28T02:30:50.132902551Z",
"provider": "osv",
"references": [
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"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m758-wjhj-p3jq",
"https://nvd.nist.gov/vuln/detail/CVE-2026-34943"
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"security_relevant": true,
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"source_id": "core-osv",
"document_id": 518296,
"published_at": "2026-04-09T18:36:51.37+00:00"
}