CVE-2022-31169

Wasmtime is a standalone runtime for WebAssembly. There is a bug in Wasmtime's code generator, Cranelift, for AArch64 targets where constant divisors can result in incorrect division results at runtime. This affects Wasmtime prior to version 0.38.2 and Cranelift prior to 0.85.2. This issue only affects the AArch64 platform. Other platforms are not affected. The translation rules for constants did not take into account whether sign or zero-extension should happen which resulted in an incorrect value being placed into a register when a division was encountered. The impact of this bug is that programs executing within the WebAssembly sandbox would not behave according to the WebAssembly specification. This means that it is hypothetically possible for execution within the sandbox to go awry and WebAssembly programs could produce unexpected results. This should not impact hosts executing WebAssembly but does affect the correctness of guest programs. This bug has been patched in Wasmtime version 0.38.2 and cranelift-codegen 0.85.2. There are no known workarounds.

Wasmtime is a standalone runtime for WebAssembly. There is a bug in Wasmtime's code generator, Cranelift, for AArch64 targets where constant divisors can result in incorrect division results at runtime. This affects Wasmtime prior to version 0.38.2 and Cranelift prior to 0.85.2. This issue only affects the AArch64 platform. Other platforms are not affected. The translation rules for constants did not take into account whether sign or zero-extension should happen which resulted in an incorrect value being placed into a register when a division was encountered. The impact of this bug is that programs executing within the WebAssembly sandbox would not behave according to the WebAssembly specification. This means that it is hypothetically possible for execution within the sandbox to go awry and WebAssembly programs could produce unexpected results. This should not impact hosts executing WebAssembly but does affect the correctness of guest programs. This bug has been patched in Wasmtime version 0.38.2 and cranelift-codegen 0.85.2. There are no known workarounds.

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-7f6x-jwh5-m9r4. For more information see the GitHub-hosted security advisory.

### Impact There was a bug in Wasmtime's code generator, Cranelift, for AArch64 targets where constant divisors could result in incorrect division results at runtime. The translation rules for constants did not take into account whether sign- or zero-extension should happen, which resulted in an incorrect value being placed into a register when a division was encountered. For example, a constant 32-bit unsigned divisor of `0xfffffffe` would be incorrectly sign-extended to 64-bits to `0xfffffffffffffffe`. Any kind of division of operands smaller than 64 bits is implemented with a 64-bit division instruction which would then result in an incorrect result because the divisor was larger than expected. The impact of this bug is that programs executing within the WebAssembly sandbox would not behave according to the WebAssembly specification. This means that it is hypothetically possible for execution within the sandbox to go awry and WebAssembly programs could produce unexpected results. This should not impact hosts executing WebAssembly, but does affect the correctness of guest programs. This bug was found with differential fuzzing of Wasmtime against other engines on the AArch64 platform. Fuzzing on AArch64 is not regularly performed at this time and the Wasmtime team is investigating how best to continuously fuzz AArch64 in the same manner as x86_64. ### Patches This bug has been patched and users should upgrade to Wasmtime version 0.38.2. ### Workarounds If upgrading is not an option at this time, direct users of Cranelift that control the exact Cranelift instructions being compiled can avoid the vulnerability by explicitly extending constant divisors to 64 bits using either the `sextend.i64` or the `uextend.i64` operation. Note, though, that this issue only affects the AArch64 targets. Other platforms are not affected. ### For more information If you have any questions or comments about this advisory: * Reach out to us on [the Bytecode Alliance Zulip chat](https://bytecodealliance.zulipchat.com/#narrow/stream/217126-wasmtime) * Open an issue in [the bytecodealliance/wasmtime repository](https://github.com/bytecodealliance/wasmtime/)

Wasmtime es un tiempo de ejecución independiente para WebAssembly. Se presenta un error en el generador de código de Wasmtime, Cranelift, para los objetivos AArch64 donde los divisores constantes pueden resultar en resultados de división incorrectos en tiempo de ejecución. Esto afecta a Wasmtime versiones anteriores a 0.38.2 y a Cranelift versiones anteriores a 0.85.2. Este problema sólo afecta a la plataforma AArch64. Las demás plataformas no están afectadas. Las reglas de traducción de las constantes no tenían en cuenta si el signo o la extensión cero debían producirse, lo que resultaba en la colocación de un valor incorrecto en un registro cuando era encontrada una división. El impacto de este bug es que los programas que son ejecutados dentro del sandbox de WebAssembly no son comportados de acuerdo con la especificación de WebAssembly. Esto significa que es hipotéticamente posible que la ejecución dentro del sandbox sea desviado y los programas WebAssembly puedan producir resultados no esperados. Esto no debería afectar a los hosts que ejecutan WebAssembly, pero sí a la corrección de los programas invitados. Este error ha sido parcheado en Wasmtime versión 0.38.2 y en cranelift-codegen versión 0.85.2. No se presentan mitigaciones conocidas