CVE-2020-1093 in Internet Explorer
Summary
by MITRE
A remote code execution vulnerability exists in the way that the VBScript engine handles objects in memory, aka 'VBScript Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2020-1035, CVE-2020-1058, CVE-2020-1060.
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Analysis
by VulDB Data Team • 10/16/2020
The vulnerability identified as CVE-2020-1093 represents a critical remote code execution flaw within Microsoft's VBScript engine implementation. This vulnerability specifically targets the manner in which the engine manages object references in memory, creating an exploitable condition that allows attackers to execute arbitrary code on affected systems. The flaw exists in the scripting engine's memory management mechanisms, particularly when processing certain VBScript objects that are manipulated in ways that trigger memory corruption conditions. Security researchers have classified this as a remote code execution vulnerability due to its ability to be exploited over network connections without requiring user interaction, making it particularly dangerous in enterprise environments where scripting engines are frequently utilized for automation and system management tasks.
The technical nature of this vulnerability stems from improper handling of object references during memory operations within the VBScript engine. When the engine processes specific VBScript code sequences that involve object manipulation, particularly those that create or modify object references in memory, it fails to properly validate or sanitize these operations. This leads to memory corruption conditions that can be leveraged by attackers to inject and execute malicious code. The vulnerability manifests when the engine encounters certain object types that, when manipulated through specific sequences, cause buffer overflows or other memory corruption scenarios. These memory corruption conditions can be triggered through various attack vectors including web-based exploitation, email attachments, or malicious documents that contain crafted VBScript code. The flaw is categorized under CWE-125 as an out-of-bounds read condition and CWE-787 as an out-of-bounds write condition, representing the core memory safety issues that enable the remote code execution capability.
The operational impact of CVE-2020-1093 is severe and far-reaching across enterprise networks and individual systems. Organizations running affected versions of Windows operating systems are vulnerable to attacks that can result in complete system compromise, data exfiltration, and persistence mechanisms being established. The vulnerability affects systems that have VBScript enabled, which includes most Windows environments where legacy applications or system scripts rely on VBScript for execution. Attackers can leverage this vulnerability through multiple attack vectors including web browsers that execute VBScript, email clients that process documents containing malicious VBScript, or through other attack surfaces where VBScript execution is possible. The vulnerability is particularly concerning because it can be exploited remotely without user interaction, making it an ideal candidate for automated exploitation campaigns. According to ATT&CK framework, this vulnerability maps to T1059.005 for VBScript execution and T1203 for exploitation for client execution, representing the techniques attackers commonly employ to leverage such vulnerabilities in the wild.
Mitigation strategies for CVE-2020-1093 focus on immediate patching and operational security measures to reduce risk exposure. Microsoft released security updates that address this vulnerability through patches that correct the memory management issues within the VBScript engine. Organizations should prioritize deployment of these patches across all affected systems, particularly those that are internet-facing or have high-value assets. Additional mitigations include disabling VBScript execution where possible, implementing network segmentation to limit attack surface, and deploying intrusion detection systems to monitor for exploitation attempts. Security teams should also consider implementing application whitelisting policies to prevent execution of untrusted VBScript code and ensure that legacy systems are properly isolated. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates how legacy scripting technologies can pose significant security risks when not properly maintained or deprecated. Organizations should conduct comprehensive vulnerability assessments to identify systems that may be running vulnerable versions of the VBScript engine and ensure that all endpoints are properly secured against this and similar memory corruption vulnerabilities.