CVE-2020-36404 in Engine
Summary
by MITRE • 07/01/2021
Keystone Engine 0.9.2 has an invalid free in llvm_ks::SmallVectorImpl::~SmallVectorImpl.
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Analysis
by VulDB Data Team • 07/04/2021
The vulnerability identified as CVE-2020-36404 resides within the Keystone Engine version 0.9.2, a widely-used multi-platform assembler framework that enables developers to create binary code for various architectures. This particular flaw manifests as an invalid free operation within the llvm_ks::SmallVectorImpl destructor, specifically in the ~SmallVectorImpl method. The issue occurs when the destructor attempts to release memory that has already been freed or is otherwise in an invalid state, creating a potential memory corruption scenario that can lead to unpredictable behavior or system instability.
The technical root cause of this vulnerability stems from improper memory management within the SmallVector implementation used by Keystone's LLVM backend. When the destructor for SmallVectorImpl is invoked, it attempts to free memory resources without properly validating the state of the memory pointers or ensuring that the memory has not already been released through previous operations. This invalid free operation represents a classic memory safety issue that can be exploited to cause denial of service conditions or potentially enable arbitrary code execution depending on the memory layout and exploitation context. The vulnerability specifically targets the cleanup phase of the assembly engine's internal data structures, making it particularly dangerous as it can occur during normal operation when the engine processes assembly code.
The operational impact of CVE-2020-36404 extends beyond simple system crashes, as it can affect any application or service that relies on Keystone Engine 0.9.2 for code generation or binary manipulation tasks. Attackers who can control the input to the assembly engine may trigger the invalid free condition through malformed assembly code or crafted input sequences, potentially leading to application crashes, data corruption, or in more sophisticated scenarios, remote code execution. The vulnerability aligns with CWE-415, which describes improper free conditions where a program attempts to free memory that has already been freed or is not properly allocated. This type of memory corruption vulnerability can be particularly challenging to exploit reliably but represents a significant risk to systems that process untrusted assembly input or use the engine in security-sensitive contexts.
Mitigation strategies for this vulnerability primarily focus on immediate remediation through version updates to Keystone Engine 0.9.3 or later, which contains the necessary fixes for the memory management issues within the SmallVector implementation. Organizations should conduct comprehensive testing of their applications that utilize the Keystone Engine to ensure compatibility with updated versions and verify that no regression issues have been introduced. Additionally, implementing proper input validation and sanitization measures when processing assembly code can help reduce the attack surface, though this does not address the core memory management flaw. From a defensive perspective, this vulnerability demonstrates the importance of rigorous memory safety practices in systems that rely on complex memory management patterns, particularly those involving destructors and automatic resource cleanup operations. The issue also highlights the need for continuous security monitoring and patch management processes to ensure that known vulnerabilities in third-party libraries are promptly addressed.
The vulnerability's characteristics align with ATT&CK technique T1059.007, which covers the use of assembly languages for system interaction, as it affects the underlying assembly processing capabilities of the system. This makes it particularly relevant for defenders monitoring assembly code generation activities and for incident response teams investigating potential exploitation attempts. The memory safety issue also relates to broader security concerns around heap management and memory corruption vulnerabilities that are frequently targeted in advanced persistent threat campaigns and exploit development activities.