Vulnerability · Published Apr 9, 2026 · Assigned by GitHub_M
CVE-2026-34983Wasmtime has a use-after-free bug after cloning `wasmtime::Linker`
Low 1.0
In plain English
A low-severity use-after-free in wasmtime from bytecodealliance. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | rust-wasmtime | no fix listed | DEBIAN-CVE-2026-34983 |
| Debian:14 | rust-wasmtime | 36.0.7+dfsg-1 | DEBIAN-CVE-2026-34983 |
| PyPI | wasmtime | no fix listed | PYSEC-2026-151 |
| Ubuntu:24.04:LTS | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-34983 |
| Ubuntu:25.10 | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-34983 |
| Ubuntu:26.04:LTS | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-34983 |
| Ubuntu:26.10 | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-34983 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| bytecodealliance | wasmtime | >= 43.0.0, < 43.0.1 |
Weakness: CWE-416 · Vector: CVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N