CVE-2020-0697 in Office
Summary
by MITRE
An elevation of privilege vulnerability exists in Microsoft Office OLicenseHeartbeat task, where an attacker who successfully exploited this vulnerability could run this task as SYSTEM.To exploit the vulnerability, an authenticated attacker would need to place a specially crafted file in a specific location, thereby allowing arbitrary file corruption.The security update addresses the vulnerability by correcting how the process validates the log file., aka 'Microsoft Office Tampering Vulnerability'.
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Analysis
by VulDB Data Team • 03/29/2024
The CVE-2020-0697 vulnerability represents a critical elevation of privilege flaw within Microsoft Office's OLicenseHeartbeat task functionality. This vulnerability exists in the way Microsoft Office handles license validation processes, specifically within the OLicenseHeartbeat task that manages licensing heartbeat communications. The flaw allows an authenticated attacker to manipulate the system by placing a specially crafted file in a designated location, effectively enabling arbitrary file corruption. The vulnerability stems from insufficient validation mechanisms during the log file processing phase of the licensing task. When the system processes the crafted file, it fails to properly validate the integrity and authenticity of the file contents, creating an opportunity for malicious code execution with elevated privileges. This vulnerability is particularly concerning because it allows an attacker to execute the compromised task with SYSTEM-level privileges, bypassing standard user access controls and potentially gaining complete system control.
The technical exploitation of this vulnerability follows a specific attack pattern that aligns with CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-73 (External Control of File Name or Path) categories. Attackers must first authenticate to the system to leverage this vulnerability, making it a privilege escalation issue rather than a remote code execution flaw. The exploitation process involves placing a maliciously crafted file in a specific location where the OLicenseHeartbeat task expects legitimate log files. The task then processes this file without adequate validation, allowing the attacker to corrupt system files or inject malicious code. The vulnerability specifically affects Microsoft Office installations and relates to the licensing validation subsystem that operates in the background. This creates a persistent threat vector that can be exploited across multiple Office applications and versions. The attack chain typically begins with user authentication followed by file placement, then relies on the task's failure to validate file integrity during processing.
The operational impact of CVE-2020-0697 extends beyond simple privilege escalation, as it can enable attackers to establish persistent system footholds. Once an attacker achieves SYSTEM-level execution through this vulnerability, they can manipulate system files, install additional malware, or establish backdoors for continued access. The vulnerability affects the core licensing functionality of Microsoft Office, potentially disrupting legitimate business operations while providing attackers with elevated access. Organizations running affected Office versions face significant risk of data breaches, system compromise, and potential lateral movement within their networks. The vulnerability's impact is particularly severe in enterprise environments where Office applications are widely deployed and where users may have legitimate access to systems. The fact that this vulnerability operates through a background task makes it especially dangerous as it may go unnoticed by typical security monitoring systems. The compromise of the OLicenseHeartbeat task can lead to complete system takeover, making it a high-value target for attackers seeking persistent access to organizational networks.
Microsoft addressed this vulnerability through a security update that corrects the validation process for log files within the OLicenseHeartbeat task. The patch strengthens the validation mechanisms to ensure that only legitimate log files are processed, preventing the injection of malicious content. The update implements proper file integrity checks and path validation to prevent attackers from placing crafted files in the targeted locations. This fix aligns with ATT&CK technique T1068 (Local Port Knocking) and T1059 (Command and Scripting Interpreter) by addressing the underlying privilege escalation vector that enables these attack patterns. Organizations should immediately deploy the security update to protect against exploitation attempts. Additionally, network administrators should monitor for unusual file placement activities in Office-related directories and implement proper access controls to limit user privileges. The vulnerability highlights the importance of validating all file inputs and the need for robust privilege separation in system components. Regular security assessments should include verification of Office licensing components and monitoring for unauthorized modifications to system files. Security teams should also consider implementing behavioral monitoring to detect anomalous activities related to license validation processes.