CVE-2019-0842 in Windows
Summary
by MITRE
A remote code execution vulnerability exists in the way that the VBScript engine handles objects in memory, aka 'Windows VBScript Engine Remote Code Execution Vulnerability'.
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Analysis
by VulDB Data Team • 07/12/2024
The vulnerability identified as CVE-2019-0842 represents a critical remote code execution flaw within the Windows VBScript engine implementation. This vulnerability specifically targets how the scripting engine manages object references in memory, creating a pathway for malicious actors to execute arbitrary code on affected systems. The issue stems from improper handling of object lifecycle management and memory allocation within the VBScript interpreter, which is a core component of the Windows operating system's scripting infrastructure. Security researchers have classified this as a remote code execution vulnerability due to its ability to be exploited through remote attack vectors without requiring local system access.
The technical root cause of this vulnerability lies in the VBScript engine's insufficient validation of object references during memory operations. When the engine processes certain VBScript code containing maliciously crafted object manipulation sequences, it fails to properly validate memory pointers and object handles, leading to memory corruption conditions. This memory corruption can be leveraged to overwrite critical memory regions, including return addresses and function pointers, enabling attackers to redirect execution flow to malicious code. The vulnerability manifests particularly when VBScript objects are created, manipulated, and destroyed in specific sequences that trigger buffer overflows or use-after-free conditions. This flaw is categorized under CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write conditions, both of which are common in memory safety violations.
The operational impact of CVE-2019-0842 is severe and far-reaching across Windows environments, particularly affecting systems running Windows 7, Windows 8.1, Windows Server 2008, and Windows Server 2012. Attackers can exploit this vulnerability through various attack vectors including malicious websites, email attachments, or compromised web applications that execute VBScript code. The vulnerability is particularly dangerous because VBScript is enabled by default in many Windows environments, and the exploitation can occur without user interaction in certain scenarios. Once successfully exploited, the vulnerability allows attackers to gain full system compromise, potentially leading to data exfiltration, lateral movement within networks, and establishment of persistent backdoors. The attack surface is broad as VBScript is commonly used in enterprise environments for automation scripts, legacy applications, and system administration tasks, making this vulnerability a prime target for advanced persistent threat actors.
Organizations should prioritize immediate mitigation through Microsoft's security patches, specifically the cumulative update released in the July 2019 security bulletin. The recommended approach includes deploying the latest Windows updates and implementing additional security controls such as disabling VBScript execution in Internet Explorer through group policy settings or registry modifications. Network segmentation and application whitelisting can provide additional defense-in-depth layers to limit the potential impact of exploitation attempts. Security monitoring should focus on detecting unusual script execution patterns, particularly in web browsers and email clients, as well as anomalous memory access patterns that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.005 for command and scripting interpreter, specifically targeting VBScript execution, and T1203 for exploitation for execution, making it a significant concern for organizations following MITRE ATT&CK framework assessments. Organizations should also consider implementing browser isolation technologies and enhanced email security controls to reduce the risk of successful exploitation through web-based attack vectors.