CVE-2026-34942 MEDIUM

CVE-2026-34942: Wasmtime panics when transcoding misaligned utf-16 strings

Vendor Bytecodealliance
Product wasmtime
Weakness CWE-129
Published April 9, 2026
Last update April 9, 2026

CVSS base score

5.9/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction
Confidentiality
Integrity

CVSS vector

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

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's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. 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 9, 2026 Record updated