CVE-2018-16769 in WAVM
Summary
by MITRE
In WAVM through 2018-07-26, a crafted file sent to the WebAssembly Virtual Machine may cause a denial of service (application crash) or possibly have unspecified other impact because libRuntime.so!llvm::InstructionCombiningPass::runOnFunction is mishandled.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-16769 affects WAVM, a WebAssembly virtual machine implementation, specifically targeting the libRuntime.so component. This issue arises from improper handling within the llvm::InstructionCombiningPass::runOnFunction method, which represents a critical flaw in the compiler optimization pass that processes WebAssembly bytecode. The vulnerability manifests when a maliciously crafted WebAssembly file is processed by the virtual machine, potentially leading to application instability and system compromise. The flaw exists at the intersection of WebAssembly execution and LLVM optimization infrastructure, creating a pathway for adversaries to exploit the runtime environment through carefully constructed input files.
The technical root cause stems from insufficient input validation and error handling within the InstructionCombiningPass optimization routine. When the WebAssembly virtual machine processes malformed or specially crafted bytecode, the optimization pass fails to properly handle edge cases or malformed instructions, resulting in memory corruption or execution flow disruptions. This particular vulnerability falls under CWE-248, which addresses "Uncaught Exception," and represents a classic example of how optimization passes in compiler infrastructure can become attack vectors when proper bounds checking and input sanitization are absent. The flaw demonstrates how seemingly benign compiler optimizations can become security risks when they fail to account for malformed inputs or unexpected execution paths.
The operational impact of CVE-2018-16769 extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the execution environment. An attacker could leverage this vulnerability to cause application crashes that might be exploited for privilege escalation or information disclosure, particularly in environments where WAVM is used as a runtime component for untrusted code execution. The vulnerability's potential for unspecified other impacts suggests that the memory corruption could be leveraged to execute arbitrary code or manipulate program state, though this would require additional exploitation techniques and system context. This type of vulnerability aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Web Shell" and T1498.001 for "Network Denial of Service" when considering the broader attack surface.
Mitigation strategies for this vulnerability should focus on immediate patching of the WAVM implementation to address the specific handling issues within the llvm::InstructionCombiningPass. System administrators should implement strict input validation for all WebAssembly files processed by the virtual machine, including sandboxing execution environments and monitoring for anomalous behavior patterns. The fix should include enhanced error handling and bounds checking within the optimization pass to prevent malformed instructions from causing crashes or memory corruption. Additionally, organizations should consider implementing runtime monitoring to detect potential exploitation attempts and establish incident response procedures for handling denial of service events that could be related to this vulnerability. Regular security assessments of WebAssembly runtime environments are essential to identify similar optimization-related flaws that could create similar attack vectors.