Vulnerabilities > CVE-2022-31104 - Incorrect Calculation vulnerability in Bytecodealliance Cranelift-Codegen and Wasmtime

047910
CVSS 5.6 - MEDIUM
Attack vector
NETWORK
Attack complexity
HIGH
Privileges required
NONE
Confidentiality impact
LOW
Integrity impact
LOW
Availability impact
LOW
network
high complexity
bytecodealliance
CWE-682
NVD
Published: 2022-06-28
Updated: 2022-07-08

Summary

Wasmtime is a standalone runtime for WebAssembly. In affected versions wasmtime's implementation of the SIMD proposal for WebAssembly on x86_64 contained two distinct bugs in the instruction lowerings implemented in Cranelift. The aarch64 implementation of the simd proposal is not affected. The bugs were presented in the `i8x16.swizzle` and `select` WebAssembly instructions. The `select` instruction is only affected when the inputs are of `v128` type. The correspondingly affected Cranelift instructions were `swizzle` and `select`. The `swizzle` instruction lowering in Cranelift erroneously overwrote the mask input register which could corrupt a constant value, for example. This means that future uses of the same constant may see a different value than the constant itself. The `select` instruction lowering in Cranelift wasn't correctly implemented for vector types that are 128-bits wide. When the condition was 0 the wrong instruction was used to move the correct input to the output of the instruction meaning that only the low 32 bits were moved and the upper 96 bits of the result were left as whatever the register previously contained (instead of the input being moved from). The `select` instruction worked correctly if the condition was nonzero, however. This bug in Wasmtime's implementation of these instructions on x86_64 represents an incorrect implementation of the specified semantics of these instructions according to the WebAssembly specification. The impact of this is benign for hosts running WebAssembly but represents possible vulnerabilities within the execution of a guest program. For example a WebAssembly program could take unintended branches or materialize incorrect values internally which runs the risk of exposing the program itself to other related vulnerabilities which can occur from miscompilations. We have released Wasmtime 0.38.1 and cranelift-codegen (and other associated cranelift crates) 0.85.1 which contain the corrected implementations of these two instructions in Cranelift. If upgrading is not an option for you at this time, you can avoid the vulnerability by disabling the Wasm simd proposal. Additionally the bug is only present on x86_64 hosts. Other aarch64 hosts are not affected. Note that s390x hosts don't yet implement the simd proposal and are not affected.

Vulnerable Configurations

Part Description Count
Application
Bytecodealliance
125

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Attack through Shared Data
    An attacker exploits a data structure shared between multiple applications or an application pool to affect application behavior. Data may be shared between multiple applications or between multiple threads of a single application. Data sharing is usually accomplished through mutual access to a single memory location. If an attacker can manipulate this shared data (usually by co-opting one of the applications or threads) the other applications or threads using the shared data will often continue to trust the validity of the compromised shared data and use it in their calculations. This can result in invalid trust assumptions, corruption of additional data through the normal operations of the other users of the shared data, or even cause a crash or compromise of the sharing applications.
  • Integer Attacks
    An attacker takes advantage of the structure of integer variables to cause these variables to assume values that are not expected by an application. For example, adding one to the largest positive integer in a signed integer variable results in a negative number. Negative numbers may be illegal in an application and the application may prevent an attacker from providing them directly, but the application may not consider that adding two positive numbers can create a negative number do to the structure of integer storage formats.
  • Pointer Attack
    This attack involves an attacker manipulating a pointer within a target application resulting in the application accessing an unintended memory location. This can result in the crashing of the application or, for certain pointer values, access to data that would not normally be possible or the execution of arbitrary code. Since pointers are simply integer variables, Integer Attacks may often be used in Pointer Attacks.

References