CVE-2021-45929 in Wasm3
Summary
by MITRE • 01/01/2022
Wasm3 0.5.0 has an out-of-bounds write in CompileBlock (called from CompileElseBlock and Compile_If).
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Analysis
by VulDB Data Team • 01/05/2022
The vulnerability identified as CVE-2021-45929 affects Wasm3 version 0.5.0, a WebAssembly interpreter implementation that provides runtime execution capabilities for WebAssembly modules. This issue manifests as an out-of-bounds write condition within the compilation phase of WebAssembly code execution, specifically within the CompileBlock function which serves as a critical component in the interpreter's compilation pipeline. The flaw is particularly concerning because it originates from the core compilation logic that translates WebAssembly bytecode into executable machine code, making it a fundamental security concern for any system utilizing this interpreter.
The technical flaw occurs when the CompileBlock function processes conditional constructs within WebAssembly modules, particularly when handling else blocks and if statements. The vulnerability is triggered during the compilation phase when the interpreter attempts to write data beyond the allocated memory boundaries of internal data structures used to represent compiled code blocks. This out-of-bounds write vulnerability is exacerbated by the fact that CompileBlock is invoked from both CompileElseBlock and Compile_If functions, creating multiple potential entry points for exploitation. The issue stems from inadequate bounds checking within the memory management routines that handle the compilation of conditional control flow structures in WebAssembly modules.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can potentially allow attackers to execute arbitrary code on systems running affected versions of Wasm3. Since the vulnerability occurs during the compilation phase rather than execution, an attacker could craft malicious WebAssembly modules that, when processed by the interpreter, trigger the out-of-bounds write condition. This could lead to denial of service through application crashes, memory corruption that might enable privilege escalation, or potentially remote code execution depending on the specific memory layout and system architecture. The vulnerability affects any application that relies on Wasm3 for WebAssembly module compilation and execution, particularly those in environments where untrusted WebAssembly code might be processed.
Mitigation strategies for CVE-2021-45929 should prioritize immediate upgrade to patched versions of Wasm3 where available, as this represents a critical security flaw in the interpreter's core functionality. Organizations should implement strict input validation and sanitization for any WebAssembly modules processed through Wasm3, particularly when dealing with untrusted content. Additionally, deployment of runtime monitoring and anomaly detection systems can help identify potential exploitation attempts by monitoring for unusual memory access patterns or compilation behaviors. The vulnerability aligns with CWE-787 Out-of-bounds Write, which is classified under the broader category of memory safety issues, and may be leveraged by adversaries following ATT&CK technique T1059.007 for command and scripting interpreter. System administrators should also consider implementing sandboxing mechanisms and privilege separation to limit the potential impact of successful exploitation attempts, while maintaining regular security assessments to identify similar vulnerabilities in other interpreter implementations.