Out-of-bounds write in Wasmtime - CVE-2026-34971
Published: April 10, 2026
Vulnerability identifier: #VU125762
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-34971
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Bytecode Alliance
Affected software:
Wasmtime
Wasmtime
Detailed vulnerability description
The vulnerability allows a remote user to read and write arbitrary host memory.
The vulnerability exists due to incorrect instruction lowering in Cranelift on aarch64 when compiling certain guest heap accesses. A remote user can execute a crafted WebAssembly module to read and write arbitrary host memory.
Only 64-bit WebAssembly linear memories are affected, and exploitation requires spectre mitigations or signals-based-traps to be disabled.
How to mitigate CVE-2026-34971
Install security update from vendor's website.