CVE-2018-0755 in Windows
Summary
by MITRE
The Microsoft Windows Embedded OpenType (EOT) font engine in Microsoft Windows 7 SP1 and Windows Server 2008 R2 allows information disclosure, due to how the Windows EOT font engine handles embedded fonts, aka "Windows EOT Font Engine Information Disclosure Vulnerability". This CVE ID is unique from CVE-2018-0760, CVE-2018-0761, and CVE-2018-0855.
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Analysis
by VulDB Data Team • 02/03/2021
The vulnerability identified as CVE-2018-0755 represents a critical information disclosure flaw within the Microsoft Windows Embedded OpenType (EOT) font engine that affects Windows 7 Service Pack 1 and Windows Server 2008 R2 systems. This vulnerability stems from improper handling of embedded font data within the EOT format, which is a proprietary font format developed by Microsoft for web and embedded applications. The flaw exists in the core font rendering engine that processes EOT files, creating a potential pathway for attackers to extract sensitive information from the system through crafted malicious font files. The vulnerability is particularly concerning because it operates at the operating system level within the font engine component, making it difficult to detect and isolate from typical application-level security measures. The EOT font format is commonly used in web applications and embedded systems where font rendering is critical for user interface presentation, and this vulnerability affects the fundamental way Windows processes these font resources.
The technical implementation of this vulnerability involves the EOT font engine's inadequate validation and processing of embedded font data structures, specifically when handling certain font table contents and metadata within EOT files. When a malicious EOT font file is processed by the Windows font engine, the improper memory handling and lack of sufficient bounds checking allows for information leakage from adjacent memory regions. This occurs because the font engine does not properly sanitize the font data before processing, enabling attackers to craft specific EOT files that trigger memory access patterns which expose sensitive data such as kernel memory contents, stack data, or other system resources. The vulnerability operates through a classic buffer overread or improper memory access pattern where the font engine attempts to parse font data without adequate boundary checks, potentially revealing information that should remain confidential. This type of vulnerability falls under the Common Weakness Enumeration category CWE-125, which describes out-of-bounds read conditions that can lead to information exposure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential access to system internals that could facilitate more sophisticated attacks. An attacker who successfully exploits this vulnerability could potentially gather kernel memory dumps, stack contents, or other sensitive system information that could be used to develop additional exploits or bypass security mechanisms. The attack surface is broad since EOT fonts can be embedded in various web applications, documents, and system components, making the attack vector accessible through multiple entry points. The vulnerability is particularly dangerous in enterprise environments where Windows 7 and Server 2008 R2 systems may still be operational, as these older systems are often not updated regularly and represent significant security risks. The information disclosure could potentially reveal system configuration details, memory layout information, or other sensitive data that would aid in developing more targeted attacks against the affected systems. This vulnerability aligns with ATT&CK technique T1059.007 for Windows Command Shell and T1068 for Exploitation for Privilege Escalation, as the information leakage could provide attackers with the knowledge needed to escalate privileges or develop more sophisticated attack vectors.
Mitigation strategies for CVE-2018-0755 should focus on both immediate patching and operational security measures. Microsoft released security updates that address this vulnerability through proper validation of EOT font data and improved memory handling within the font engine component. Organizations should prioritize applying the relevant security patches as soon as possible, particularly given that Windows 7 and Server 2008 R2 are no longer supported with regular security updates. Additional operational mitigations include implementing strict font file validation policies, restricting the execution of EOT fonts from untrusted sources, and monitoring for unusual font processing activities that might indicate exploitation attempts. Network-level controls such as web application firewalls and content filtering systems can help prevent the delivery of malicious EOT files to affected systems. System administrators should also consider disabling font rendering for untrusted content where possible and implementing comprehensive monitoring for memory access patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory safety practices in system-level components, emphasizing that even fundamental operating system services require robust security controls to prevent information disclosure attacks that could compromise entire systems.