CVE-2019-1111 in Excel
Summary
by MITRE
A remote code execution vulnerability exists in Microsoft Excel software when the software fails to properly handle objects in memory, aka 'Microsoft Excel Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2019-1110.
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Analysis
by VulDB Data Team • 07/02/2020
The vulnerability identified as CVE-2019-1111 represents a critical remote code execution flaw within Microsoft Excel software that stems from improper handling of objects in memory. This vulnerability specifically affects Microsoft Excel applications running on Windows operating systems and poses significant security risks to enterprise environments where spreadsheet processing is prevalent. The flaw manifests when Excel encounters malformed or specially crafted objects during normal processing operations, leading to potential system compromise through remote exploitation. Security researchers have classified this issue as a severe threat due to its remote execution capabilities and the widespread use of Excel across corporate networks. The vulnerability impacts multiple versions of Microsoft Office including Excel 2007, 2010, 2013, 2016, and 2019, making it particularly concerning for organizations with legacy systems. This issue is categorized under CWE-125 as "Out-of-bounds Read" and aligns with ATT&CK technique T1203 "Exploitation for Client Execution" which describes how attackers exploit software vulnerabilities to execute malicious code on target systems. The memory handling flaw allows attackers to manipulate object references and trigger buffer overflows or other memory corruption conditions that can be leveraged for privilege escalation and system compromise.
The technical exploitation of CVE-2019-1111 occurs when a user opens a specially crafted Excel file containing malicious objects that trigger the memory handling error. The vulnerability exploits the way Excel processes certain file formats and object references within spreadsheet documents, particularly when dealing with complex formulas or embedded objects. Attackers can craft malicious Excel files that contain malformed object structures which, when opened by an affected Excel version, cause the application to improperly handle memory allocation and object references. This improper memory management creates opportunities for attackers to inject and execute arbitrary code within the context of the Excel process. The flaw is particularly dangerous because it can be triggered through simple file opening operations without requiring additional user interaction beyond the initial document opening. The vulnerability operates at the memory management level, where object references are not properly validated or sanitized, allowing attackers to manipulate the application's memory space and potentially gain complete control over the affected system. This type of vulnerability falls under the category of heap-based buffer overflow conditions and represents a classic example of how improper memory handling can lead to remote code execution.
The operational impact of CVE-2019-1111 extends far beyond individual system compromise, as it can enable attackers to establish persistent access within enterprise networks. Organizations using affected Excel versions face significant risk of data breaches, system infiltration, and potential lateral movement throughout their network infrastructure. The vulnerability's remote execution capability means that attackers can exploit it without physical access to target systems, making it particularly dangerous for organizations with remote workers or cloud-based collaboration environments. Successful exploitation can result in complete system compromise, allowing attackers to install backdoors, exfiltrate sensitive data, or deploy additional malware. The impact is amplified by Excel's widespread use in business environments where users frequently open files from untrusted sources, including email attachments, shared network drives, and web downloads. Organizations may experience significant operational disruption, regulatory compliance issues, and potential financial losses due to the breach of sensitive corporate data. The vulnerability's exploitation can also lead to denial of service conditions, where affected systems become unusable due to memory corruption or process crashes. Security teams must implement immediate mitigation measures to protect against this vulnerability, as the attack surface is broad and the exploitation methods are well-documented.
Mitigation strategies for CVE-2019-1111 should include immediate deployment of Microsoft security patches and updates to affected Excel installations. Organizations should implement strict email filtering and attachment scanning protocols to prevent malicious Excel files from reaching end users. Network segmentation and application whitelisting can help reduce the attack surface by limiting where potentially malicious files can be executed. Security teams should also consider implementing macro security policies that disable or restrict the execution of macros in Excel documents. Regular security awareness training for employees can help reduce the risk of accidental exploitation through social engineering attacks that deliver malicious Excel files. System monitoring and intrusion detection should be enhanced to identify potential exploitation attempts, particularly around file opening operations and memory access patterns. The implementation of endpoint protection solutions with behavioral monitoring capabilities can help detect anomalous Excel process behavior that may indicate exploitation attempts. Organizations should also establish incident response procedures specifically for dealing with Excel-based vulnerabilities and maintain up-to-date backups of critical systems to facilitate recovery in case of successful exploitation. Regular vulnerability assessments and penetration testing should be conducted to identify and remediate similar memory handling issues within the organization's software ecosystem. The vulnerability demonstrates the critical importance of proper memory management in application security and highlights the need for continuous security testing and monitoring to detect and prevent similar issues from being exploited in the future.