CVE-2023-27477
Description
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 instruction which causes incorrect results to be returned if lanes are selected from the second vector. This codegen bug has been fixed in Wasmtiem 6.0.1, 5.0.1, and 4.0.1. Users are recommended to upgrade to these updated versions. If upgrading is not an option for you at this time, you can avoid this miscompilation by disabling the Wasm simd proposal. Additionally the bug is only present on x86_64 hosts. Other platforms such as AArch64 and s390x are not affected.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
wasmtimecrates.io | >= 1.0.0, < 4.0.1 | 4.0.1 |
wasmtimecrates.io | >= 5.0.0, < 5.0.1 | 5.0.1 |
wasmtimecrates.io | >= 6.0.0, < 6.0.1 | 6.0.1 |
cranelift-codegencrates.io | >= 0.88.0, < 0.91.1 | 0.91.1 |
cranelift-codegencrates.io | >= 0.92.0, < 0.92.1 | 0.92.1 |
cranelift-codegencrates.io | >= 0.93.0, < 0.93.1 | 0.93.1 |
Affected products
1- Range: cranelift-codegen: >= 0.88.0, < 0.91.1
Patches
15dc2bbccbb36Merge pull request from GHSA-xm67-587q-r2vw
3 files changed · +10 −2
cranelift/codegen/src/isa/x64/lower/isle.rs+1 −1 modified@@ -752,7 +752,7 @@ impl Context for IsleContext<'_, '_, MInst, X64Backend> { fn shuffle_0_31_mask(&mut self, mask: &VecMask) -> VCodeConstant { let mask = mask .iter() - .map(|&b| if b > 15 { b.wrapping_sub(15) } else { b }) + .map(|&b| if b > 15 { b.wrapping_sub(16) } else { b }) .map(|b| if b > 15 { 0b10000000 } else { b }) .collect(); self.lower_ctx
cranelift/filetests/filetests/isa/x64/simd-lane-access-compile.clif+2 −1 modified@@ -101,7 +101,8 @@ block0: ; addb %al, (%rax) ; addb %al, (%rax) ; addb %al, (%rax) -; addb %al, (%rcx, %rax) +; addb %al, (%rbx) +; addl %eax, (%rax) ; addb %al, (%rax) ; addb %al, (%rax) ; addb %al, (%rax)
cranelift/filetests/filetests/runtests/simd-shuffle.clif+7 −0 modified@@ -19,3 +19,10 @@ block0(v0: i8x16, v1: i8x16): return v2 } ; run: %shuffle_zeros([1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16], [17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32]) == [4 1 0 0 5 7 13 12 24 14 25 5 3 0 18 6] + +function %shuffle1(i8x16) -> i8x16 { +block0(v0: i8x16): + v1 = shuffle v0, v0, [8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23] + return v1 +} +; run: %shuffle1([0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15]) == [8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7]
Vulnerability mechanics
Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
7- github.com/advisories/GHSA-xm67-587q-r2vwghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2023-27477ghsaADVISORY
- docs.rs/wasmtime/latest/wasmtime/struct.Config.htmlghsaWEB
- github.com/bytecodealliance/wasmtime/commit/5dc2bbccbb363e474d2c9a1b8e38a89a43bbd5d1ghsaWEB
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xm67-587q-r2vwghsaWEB
- groups.google.com/a/bytecodealliance.org/g/sec-announce/c/Mov-ItrNJsQghsaWEB
- rustsec.org/advisories/RUSTSEC-2023-0093.htmlghsaWEB
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