CVE-2023-27477 — wasmtime is a fast and secure runtime for WebAssembly

wasmtime is a fast and secure runtime for WebAssembly. Wasmtime's code generation backend, Cranelift, has a bug on x86_64 platforms for the WebAssembly `i8x16.select` instruction which will produce the wrong results when the same operand is provided to the instruction and so

01What is this vulnerability?

wasmtime is a fast and secure runtime for WebAssembly. Wasmtime's code generation backend, Cranelift, has a bug on x86_64 platforms for the WebAssembly `i8x16.select` instruction which will produce the wrong results when the same operand is provided to the instruction and some of the selected indices are greater than 16. There is an off-by-one error in the calculation of the mask to the `pshufb`…

02Affected products

Vendor	Product	Versions
bytecodealliance	wasmtime	cranelift-codegen: >= 0.88.0, < 0.91.1, cranelift-codegen: >= 0.92.0, < 0.92.1, cranelift-codegen: >= 0.93.0, < 0.93.1, wasmtime: >= 0.37.0, < 4.0.1, wasmtime: >= 5.0.0, < 5.0.1, wasmtime: >= 6.0.0, < 6.0.1

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-03-08T00:00:00.000Z
• Last modified: 2025-02-25T14:59:59.689Z

09References

• docs.rs — https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.wasm_simd
• github.com — https://github.com/webassembly/simd
• groups.google.com — https://groups.google.com/a/bytecodealliance.org/g/sec-announce/c/Mov-ItrNJsQ
• github.com — https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xm67-587q-…
• github.com — https://github.com/bytecodealliance/wasmtime/commit/5dc2bbccbb363e474d2c9a1b8e38…