CVE-2019-1093 in Windows
Summary
by MITRE
An information disclosure vulnerability exists when DirectWrite improperly discloses the contents of its memory, aka 'DirectWrite Information Disclosure Vulnerability'. This CVE ID is unique from CVE-2019-1097.
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Analysis
by VulDB Data Team • 07/02/2020
The CVE-2019-1093 vulnerability represents a critical information disclosure flaw within Microsoft's DirectWrite graphics rendering engine that operates at the core of Windows operating systems. This vulnerability specifically affects how DirectWrite handles memory management and data exposure during text rendering operations, creating potential pathways for unauthorized access to sensitive memory contents. The flaw manifests when the graphics subsystem fails to properly sanitize memory regions, allowing malicious actors to potentially extract confidential data that should remain protected within the application's memory space.
DirectWrite serves as a core component of Windows' graphics infrastructure, responsible for rendering text and graphics in applications across the operating system. When processing text rendering requests, DirectWrite maintains various memory buffers containing both application data and system information. The vulnerability arises from improper memory boundary checking and insufficient data sanitization during these rendering operations. Attackers can exploit this weakness by crafting specific text rendering inputs that cause DirectWrite to expose memory contents that should remain private, potentially revealing sensitive information such as application state data, cryptographic keys, or other confidential system information stored in memory.
The operational impact of this vulnerability extends across multiple Windows platforms including Windows 10, Windows Server 2016, and Windows Server 2019, making it particularly concerning for enterprise environments. Security researchers have identified that this vulnerability could enable attackers to perform memory scraping operations that might reveal information about running processes, application memory structures, or even sensitive cryptographic material. The flaw is particularly dangerous when combined with other exploitation techniques, as it can provide attackers with additional information needed to conduct more sophisticated attacks. This type of information disclosure vulnerability aligns with CWE-200, which specifically addresses "Information Exposure" and represents a fundamental weakness in how systems handle sensitive data exposure.
From an adversarial perspective, this vulnerability fits within the broader ATT&CK framework under the Information Gathering tactic, specifically targeting the Collection sub-technique where attackers seek to extract sensitive information from compromised systems. The vulnerability's exploitation typically requires minimal privileges and can be executed through standard application interactions, making it particularly dangerous in environments where users have access to applications that utilize DirectWrite. The attack surface is broad since DirectWrite is integrated into numerous Windows applications and services, including web browsers, document viewers, and system utilities. Organizations may face significant risk from this vulnerability, as it can potentially expose sensitive data that could be used for further attacks or espionage activities.
Mitigation strategies for CVE-2019-1093 primarily focus on applying Microsoft's security updates and patches as soon as they become available. System administrators should prioritize patch deployment across all affected Windows systems, particularly those handling sensitive data or operating in high-risk environments. Additional defensive measures include implementing application whitelisting policies to restrict potentially vulnerable applications, monitoring for unusual memory access patterns, and conducting regular security assessments to identify potential exploitation attempts. Organizations should also consider network segmentation and access controls to limit the potential impact of successful exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices in graphics and rendering subsystems, highlighting how seemingly minor implementation flaws can create significant security risks that require immediate attention and remediation.