CVE-2019-1239 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-2019-1238.
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Analysis
by VulDB Data Team • 09/26/2020
The vulnerability described in CVE-2019-1239 represents a critical remote code execution flaw within Microsoft's VBScript engine implementation. This vulnerability specifically targets how the scripting engine manages object references in memory, creating a pathway for attackers to execute arbitrary code on affected systems. The issue manifests when the VBScript engine processes certain object operations that lead to memory corruption, ultimately allowing malicious actors to gain unauthorized control over vulnerable systems. The vulnerability is particularly concerning because it operates at the engine level, meaning that successful exploitation can bypass many traditional security controls and defenses that typically protect against such attacks.
The technical nature of this flaw falls under the category of memory corruption vulnerabilities, specifically addressing improper handling of object references during script execution. When VBScript objects are manipulated in certain ways, the engine fails to properly validate memory operations, leading to potential buffer overflows or arbitrary code execution opportunities. This vulnerability is classified as a heap-based memory corruption issue that can be triggered through crafted VBScript code or web-based attacks that leverage the scripting engine. The flaw exists in the parsing and execution components of the VBScript engine, making it particularly dangerous as it can be exploited through various attack vectors including malicious websites, email attachments, or compromised web applications that execute VBScript code.
The operational impact of CVE-2019-1239 extends beyond simple remote code execution, as it provides attackers with a powerful foothold for further compromise within targeted environments. Once successfully exploited, attackers can execute malicious code with the privileges of the compromised user, potentially leading to full system compromise, data exfiltration, or lateral movement within networks. The vulnerability affects systems running affected versions of Windows operating systems where VBScript is enabled, making it particularly relevant for enterprise environments that have legacy applications or systems that depend on VBScript functionality. Organizations with outdated systems or those that have not applied security patches face significant risk, as this vulnerability can be exploited through automated attack tools and is often leveraged in targeted campaigns against high-value targets.
Mitigation strategies for this vulnerability should focus on immediate patch deployment as provided by Microsoft through their regular security updates. System administrators should ensure that all affected Windows systems receive the appropriate security patches and that VBScript execution is disabled where possible through Group Policy settings or registry modifications. Network segmentation and application whitelisting can help reduce the attack surface by limiting where VBScript can be executed and preventing unauthorized code from running on critical systems. Additionally, implementing proper monitoring and detection capabilities can help identify exploitation attempts through unusual script execution patterns or memory access anomalies. Organizations should also consider disabling VBScript entirely in environments where it is not required, as this represents the most effective defense against exploitation of this class of vulnerability. The vulnerability aligns with attack patterns documented in the attack tree framework and is categorized under CWE-125 as an out-of-bounds read, while also relating to the broader category of CWE-787 as an out-of-bounds write, making it a significant concern for organizations following industry standards for vulnerability management and threat mitigation.