CVE-2017-4913 in Workstation
Summary
by MITRE
VMware Workstation (12.x prior to 12.5.3) and Horizon View Client (4.x prior to 4.4.0) contain an integer-overflow vulnerability in the True Type Font parser in the TPView.dll. On Workstation, this may allow a guest to execute code or perform a Denial of Service on the Windows OS that runs Workstation. In the case of a Horizon View Client, this may allow a View desktop to execute code or perform a Denial of Service on the Windows OS that runs the Horizon View Client. Exploitation is only possible if virtual printing has been enabled. This feature is not enabled by default on Workstation but it is enabled by default on Horizon View.
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Analysis
by VulDB Data Team • 12/26/2020
The vulnerability identified as CVE-2017-4913 represents a critical integer overflow flaw within the True Type Font parsing functionality of VMware's TPView.dll component. This vulnerability affects VMware Workstation versions 12.x prior to 12.5.3 and Horizon View Client versions 4.x prior to 4.4.0, demonstrating the widespread impact across VMware's virtualization ecosystem. The integer overflow occurs specifically within the font parser implementation, where insufficient input validation leads to predictable buffer overflows that can be exploited by malicious actors. This vulnerability is particularly concerning because it operates at the level of font rendering, a common and frequently used feature in virtualized environments, making it an attractive target for exploitation. The flaw exists in the TPView.dll library which handles font processing for virtual printing functionality, creating a direct pathway for code execution or denial of service attacks when malicious font data is processed.
The technical exploitation of this vulnerability requires leveraging the virtual printing feature, which serves as the attack vector for both affected products. In VMware Workstation, virtual printing must be explicitly enabled by users since it is disabled by default, whereas Horizon View Client has this feature enabled by default, significantly increasing the attack surface for the latter product. The integer overflow condition manifests when the font parser processes malformed True Type Font files, causing the application to allocate insufficient memory buffers that can be overwritten by attacker-controlled data. This memory corruption vulnerability can be translated into arbitrary code execution in the context of the Windows operating system running the affected VMware product. The vulnerability's classification aligns with CWE-190, which specifically addresses integer overflow conditions, and represents a classic example of how font processing libraries can become attack surfaces for privilege escalation and code execution. The attack scenario typically involves an attacker uploading or delivering a specially crafted font file that, when processed by the vulnerable font parser, triggers the integer overflow and subsequent memory corruption.
The operational impact of CVE-2017-4913 extends beyond simple denial of service scenarios to encompass full system compromise in targeted environments. For VMware Workstation installations, the vulnerability creates a potential guest-to-host escalation path where an attacker controlling a virtual machine could execute arbitrary code on the host operating system, effectively breaking the isolation that virtualization is designed to provide. This represents a significant threat to enterprise security infrastructure where virtualized environments are commonly used for development, testing, and production workloads. The Horizon View Client vulnerability is particularly severe due to its default-enabled status, meaning that organizations using VMware's desktop virtualization solution are automatically exposed to this risk without any configuration changes. The vulnerability affects Windows operating systems running the affected VMware products, making it a critical concern for enterprises that rely on Windows-based virtual desktop infrastructures. Attackers can leverage this vulnerability to establish persistent access, escalate privileges, or conduct reconnaissance activities within the virtualized environment, potentially leading to broader network compromise.
Mitigation strategies for CVE-2017-4913 primarily focus on immediate patch deployment and operational security measures to reduce exposure. VMware released patches for both Workstation and Horizon View Client versions that address the integer overflow in the TPView.dll component, with the recommended remediation being an upgrade to versions 12.5.3 or later for Workstation and 4.4.0 or later for Horizon View Client. Organizations should implement the patches as a priority, particularly for Horizon View Client installations where the vulnerability is enabled by default. Additional mitigations include disabling virtual printing functionality in Workstation environments where it is not required, and implementing network segmentation to limit potential attack vectors. Security monitoring should focus on detecting unusual font processing activities and monitoring for suspicious print job submissions that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and execution through legitimate system tools, as attackers would leverage the virtualized environment's printing functionality to execute malicious code. Organizations should also consider implementing application whitelisting policies to restrict font processing capabilities and reduce the attack surface for similar vulnerabilities in font rendering components. The vulnerability underscores the importance of regular security updates and proper configuration management in virtualized environments, particularly where features like virtual printing are enabled by default and can create unexpected security risks.