CVE-2015-0059 in Windows
Summary
by MITRE
win32k.sys in the kernel-mode drivers in Microsoft Windows Server 2008 R2 SP1, Windows 7 SP1, Windows 8, Windows 8.1, Windows Server 2012 Gold and R2, and Windows RT Gold and 8.1 allows local users to gain privileges via a crafted TrueType font, aka "TrueType Font Parsing Remote Code Execution Vulnerability."
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Analysis
by VulDB Data Team • 06/12/2025
The CVE-2015-0059 vulnerability represents a critical privilege escalation flaw within the Windows kernel-mode driver component win32k.sys, which forms part of the operating system's graphical subsystem. This vulnerability specifically affects multiple versions of Microsoft Windows including server and client operating systems from Windows 7 through Windows 8.1, making it particularly widespread in enterprise environments. The flaw manifests when the system processes TrueType font files through the win32k.sys driver, which handles user interface elements and graphics rendering in kernel space. This presents a significant security risk as it allows local attackers to execute arbitrary code with elevated privileges, potentially leading to complete system compromise.
The technical exploitation of this vulnerability occurs through a carefully crafted TrueType font file that triggers a buffer overflow condition within the win32k.sys driver during font parsing operations. When a user or application loads such a malicious font file, the kernel-mode driver fails to properly validate the font data structure, leading to memory corruption that can be leveraged to execute arbitrary code with kernel-level privileges. This type of vulnerability falls under the CWE-121 category of "Stack-based Buffer Overflow" and represents a classic example of how kernel-mode vulnerabilities can be exploited to achieve privilege escalation. The ATT&CK framework categorizes this under T1068 "Exploitation for Privilege Escalation" and T1059 "Command and Scripting Interpreter" as attackers can leverage this vulnerability to execute malicious code with system-level privileges.
The operational impact of CVE-2015-0059 extends far beyond simple local privilege escalation, as it can be exploited by attackers who have already gained a foothold on a system through other means such as phishing attacks or web-based exploits. Once an attacker successfully exploits this vulnerability, they can establish persistent access, escalate privileges to SYSTEM level, and potentially move laterally within a network environment. The vulnerability is particularly dangerous because it requires minimal user interaction beyond the loading of a malicious font file, and the exploitation occurs at the kernel level where standard user-mode protections are bypassed. This makes it extremely difficult to detect and remediate, as the malicious activity occurs at a level below traditional security monitoring capabilities.
Mitigation strategies for CVE-2015-0059 should focus on immediate patching of affected systems through Microsoft's security updates, which address the underlying buffer overflow condition in the win32k.sys driver. Organizations should also implement administrative controls such as disabling font loading from untrusted sources and monitoring for unusual font processing activities in system logs. Network segmentation and privilege separation can help limit the potential damage from successful exploitation, while endpoint detection and response solutions should be configured to monitor for kernel-mode activity patterns associated with this vulnerability. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and the risks associated with running legacy operating systems that may not receive continued security support, as these systems remain vulnerable to such kernel-mode exploitation techniques that have been well-documented in the cybersecurity community.