What’s Vulnerable › Vulnerabilities
CVE-2026-34943: Wasmtime panics when lifting `flags` component value
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-09 · updated 2026-10-26
- Weakness: CWE-248
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.
Affected products
- bytecodealliance wasmtime: before 24.0.7; from 25.0.0 before 36.0.7; from 37.0.0 before 42.0.2; from 43.0.0 before 43.0.1 — fixed in 24.0.7, 36.0.7, 42.0.2, 43.0.1
How to fix
Upgrade to a fixed version: bytecodealliance wasmtime 24.0.7, 36.0.7, 42.0.2, 43.0.1. Check the vendor advisory for mitigations.
References
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