CVE-2026-34943: CWE-248: Uncaught Exception in bytecodealliance wasmtime
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.
AI Analysis
Technical Summary
CVE-2026-34943 describes a medium severity vulnerability in Wasmtime, a WebAssembly runtime by bytecodealliance. The flaw involves an uncaught panic triggered when a flags-typed component model value is lifted into the Val type and contains bits outside the defined flag set. While the component model specifies ignoring such bits, Wasmtime instead panics, causing a denial-of-service condition. This affects only Wasmtime's lifting implementation, not the flags! macro, and only applies to flags-typed values within WIT interfaces. The vulnerability is fixed in Wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Potential Impact
The vulnerability allows a guest-controlled panic in the host runtime, which Wasmtime considers a denial-of-service (DoS) vector. This can disrupt the availability of the host environment running Wasmtime by causing unexpected panics when processing certain flags-typed values. There is no indication of code execution or data breach from the provided information.
Mitigation Recommendations
Fixed versions of Wasmtime are available: 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Users should upgrade to one of these versions to remediate the vulnerability. No other mitigation or temporary workaround is indicated in the provided data. Patch status is not explicitly stated but the presence of fixed versions implies an official fix is available.
CVE-2026-34943: CWE-248: Uncaught Exception in bytecodealliance wasmtime
Description
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.
CVSS v4.0
Score 5.6medium
Affected software
pkg:cargo/bytecodealliance/wasmtimeRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-34943 describes a medium severity vulnerability in Wasmtime, a WebAssembly runtime by bytecodealliance. The flaw involves an uncaught panic triggered when a flags-typed component model value is lifted into the Val type and contains bits outside the defined flag set. While the component model specifies ignoring such bits, Wasmtime instead panics, causing a denial-of-service condition. This affects only Wasmtime's lifting implementation, not the flags! macro, and only applies to flags-typed values within WIT interfaces. The vulnerability is fixed in Wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Potential Impact
The vulnerability allows a guest-controlled panic in the host runtime, which Wasmtime considers a denial-of-service (DoS) vector. This can disrupt the availability of the host environment running Wasmtime by causing unexpected panics when processing certain flags-typed values. There is no indication of code execution or data breach from the provided information.
Mitigation Recommendations
Fixed versions of Wasmtime are available: 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Users should upgrade to one of these versions to remediate the vulnerability. No other mitigation or temporary workaround is indicated in the provided data. Patch status is not explicitly stated but the presence of fixed versions implies an official fix is available.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-31T17:27:08.660Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d7f88c1cc7ad14da0c16f4
Added to database: 04/09/2026, 19:05:48 UTC
Last enriched: 04/17/2026, 11:52:30 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 147
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