Medium severity · published Apr 9, 2026
CVE-2026-34983
Wasmtime has a use-after-free bug after cloning `wasmtime::Linker`
5.0
CVSS
0.1%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.1% · higher than 2% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WA
wasmtime · bytecodealliance
>= 43.0.0, < 43.0.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34983
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-34983
Mitigation
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2
More from wasmtime
10.0
CVE-2024-51745
Wasmtime is a fast and secure runtime for WebAssembly
9.9
CVE-2026-115893
Wasmtime: Cranelift backend on aarch64 can jump to incorrect target on large Wasm `br_table` instruction
9.9
CVE-2026-115889
Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
9.9
CVE-2026-115384
Wasmtime 39.0.0 before 48.0.4 and 49.0.0 before 49.0.2 Stack Buffer Overflow
9.9
CVE-2026-34987
Wasmtime with Winch compiler backend on aarch64 may allow a sandbox-escaping memory access