CVE-2023-41880

Workarounds

This issue only affects x86_64 hosts and the only workaround is to either scan for this pattern in wasm modules which is nontrivial or to disable the SIMD proposal for WebAssembly. Users prior to 10.0.0 are unaffected by this vulnerability.

References

• PR which introduced this bug to Wasmtime
• Mailing list announcement

Wasmtime versions from 10.0.0 to 12.0.1 contain a miscompilation of the WebAssembly i64x2.shr_s instruction on x86_64 platforms when the shift amount is a constant value that is larger than 32. Only x86_64 is affected so all other targets are not affected by this. The miscompilation results in the instruction producing an incorrect result, namely the low 32-bits of the second lane of the vector are derived from the low 32-bits of the second lane of the input vector instead of the high 32-bits. The primary impact of this issue is that any WebAssembly program using the i64x2.shr_s with a constant shift amount larger than 32 may produce an incorrect result.

This issue is not an escape from the WebAssembly sandbox. Execution of WebAssembly guest programs will still behave correctly with respect to memory sandboxing and isolation from the host. Wasmtime considers non-spec-compliant behavior as a security issue nonetheless.

This issue was discovered through fuzzing of Wasmtime's code generator Cranelift.

CVE-2023-41880 has a CVSS score of 2.2 (Low). The vector is network-reachable, high 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 (10.0.2, 11.0.2, 12.0.2); upgrading removes the vulnerable code path.

Kodem intelligence

Wasmtime versions 10.0.2, 11.0.2, and 12.0.2 are all patched to no longer have this miscompilation.

1. What is CVE-2023-41880? CVE-2023-41880 is a low-severity security vulnerability in wasmtime (rust), affecting versions >= 10.0.0, < 10.0.2. It is fixed in 10.0.2, 11.0.2, 12.0.2.
2. How severe is CVE-2023-41880? CVE-2023-41880 has a CVSS score of 2.2 (Low). 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 versions of wasmtime are affected by CVE-2023-41880? wasmtime (rust) versions >= 10.0.0, < 10.0.2 is affected.
4. Is there a fix for CVE-2023-41880? Yes. CVE-2023-41880 is fixed in 10.0.2, 11.0.2, 12.0.2. Upgrade to this version or later.
5. Is CVE-2023-41880 exploitable, and should I be worried? Whether CVE-2023-41880 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-2023-41880 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-2023-41880?
   • Upgrade wasmtime to 10.0.2 or later
   • Upgrade wasmtime to 11.0.2 or later
   • Upgrade wasmtime to 12.0.2 or later

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