CVE-2026-34983 — MEDIUM (5.0)

Vulnerability Description

Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the new, cloned linker instance, resulting in a use-after-free. This vulnerability is fixed in 43.0.1.

CVSS Score

5.0

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

HIGH

Affected Products

Vendor	Product	Versions
Bytecodealliance	Wasmtime	43.0.0

Related Weaknesses (CWE)

CWE-416

References

https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-Vendor AdvisoryMitigation
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-Vendor AdvisoryMitigation

FAQ

What is CVE-2026-34983?

CVE-2026-34983 is a vulnerability with a CVSS score of 5.0 (MEDIUM). Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be trigg...

How severe is CVE-2026-34983?

CVE-2026-34983 has been rated MEDIUM with a CVSS base score of 5.0/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-34983?

Check the references section above for vendor advisories and patch information. Affected products include: Bytecodealliance Wasmtime.