What’s Vulnerable › Vulnerabilities

CVE-2026-34983: Wasmtime has a use-after-free bug after cloning `wasmtime::Linker`

• Severity: medium (CVSS 5.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-09 · updated 2026-10-26
• Weakness: CWE-416

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.

Affected products

• bytecodealliance wasmtime: 43.0.0

References

• https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2
• https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2

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