CVE-2026-34943 MEDIUM

CVE-2026-34943: Wasmtime panics when lifting `flags` component value

Vendor Bytecodealliance
Product wasmtime
Weakness CWE-248
Published April 9, 2026
Last update April 13, 2026

CVSS base score

5.6/10
Attack vector Network
Attack complexity High
Privileges required High
User interaction
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 9, 2026 CVE published
April 13, 2026 Record updated