CVE-2022-31146 is a medium-severity (CVSS 6.4) Use After Free vulnerability in wasmtime. A fix is available for wasmtime — see the affected versions and patch details below.
Use After Free in Wasmtime
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
wasmtime🦀cranelift-codegenReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Wasmtime is a standalone runtime for WebAssembly. There is a bug in the Wasmtime's code generator, Cranelift, where functions using reference types may be incorrectly missing metadata required for runtime garbage collection. This means that if a GC happens at runtime then the GC pass will mistakenly think these functions do not have live references to GC'd values, reclaiming them and deallocating them. The function will then subsequently continue to use the values assuming they had not been GC'd, leading later to a use-after-free. This bug was introduced in the migration to the regalloc2 register allocator that occurred in the Wasmtime 0.37.0 release on 2022-05-20. This bug has been patched and users should upgrade to Wasmtime version 0.38.2. Mitigations for this issue can be achieved by disabling the reference types proposal by passing false to wasmtime::Config::wasm_reference_types or downgrading to Wasmtime 0.36.0 or prior.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | wasmtime | ≥ 0.37.0&&< 0.38.2 | 0.38.2cargo update -p wasmtime --precise 0.38.2 |
| 🦀crates.io | cranelift-codegen | ≥ 0.84.0&&< 0.85.2 | 0.85.2cargo update -p cranelift-codegen --precise 0.85.2 |
Affected Products
cranelift-codegenbytecodealliancewasmtimebytecodeallianceDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for wasmtime, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update wasmtime to 0.38.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-31146 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Frequently Asked Questions
Is CVE-2022-31146 in your dependencies?
Find it across crates.io, including transitive dependencies.