CVE-2022-31146

There is a bug in Wasmtime's code generator, Cranelift, where functions using reference types may be incorrectly missing metadata required for runtime garbage collection (GC). This means that if a GC happens at runtime then the collector will mistakenly think some Wasm stack frames do not have live references to garbage collected values and therefore reclaim and deallocate them. The function can then subsequently continue to use the values, leading later to use-after-free bugs. This bug was introduced in Cranelift's migration to the regalloc2 register allocator 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 doing one of:

• Disabling the reference types proposal by passing false to wasmtime::Config::wasm_reference_types.
• Downgrading to Wasmtime 0.36.0 or prior.

Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.

CVE-2022-31146 has a CVSS score of 6.4 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.38.2, 0.85.2); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2022-31146? CVE-2022-31146 is a medium-severity use after free vulnerability in wasmtime (rust), affecting versions >= 0.37.0, < 0.38.2. It is fixed in 0.38.2, 0.85.2. Memory is accessed after it has been freed, leading to undefined behavior in native code.
2. How severe is CVE-2022-31146? CVE-2022-31146 has a CVSS score of 6.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2022-31146?
   • wasmtime (rust) (versions >= 0.37.0, < 0.38.2)
   • cranelift-codegen (rust) (versions >= 0.84.0, < 0.85.2)
4. Is there a fix for CVE-2022-31146? Yes. CVE-2022-31146 is fixed in 0.38.2, 0.85.2. Upgrade to this version or later.
5. Is CVE-2022-31146 exploitable, and should I be worried? Whether CVE-2022-31146 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2022-31146 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2022-31146?
   • Upgrade wasmtime to 0.38.2 or later
   • Upgrade cranelift-codegen to 0.85.2 or later