CVE-2017-4909 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 a heap buffer-overflow vulnerability in TrueType Font (TTF) 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.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 12/26/2020
This vulnerability resides in the TrueType Font parser implementation within VMware's TPView.dll component, specifically affecting VMware Workstation versions 12.x prior to 12.5.3 and Horizon View Client versions 4.x prior to 4.4.0. The heap buffer-overflow flaw occurs when processing specially crafted TTF font files, creating a critical security weakness that can be exploited to execute arbitrary code or cause denial of service conditions on Windows operating systems running these VMware products. The vulnerability is classified under CWE-121 as a heap-based buffer overflow, representing a fundamental memory corruption issue that can lead to unpredictable system behavior and potential privilege escalation. The flaw is particularly concerning because it operates within the font rendering pipeline, a common attack surface that has historically been exploited for privilege escalation and code execution attacks.
The technical exploitation of this vulnerability requires that virtual printing functionality be enabled, which serves as a crucial prerequisite for successful attack execution. In VMware Workstation, virtual printing is not enabled by default, providing a natural defense-in-depth mechanism that reduces the attack surface for this particular vulnerability. However, the Horizon View Client has virtual printing enabled by default, making it inherently more susceptible to exploitation in environments where this feature is not disabled. The attack vector involves crafting malicious TTF font files that, when processed by the vulnerable TPView.dll component, trigger the buffer overflow condition. This condition allows attackers to overwrite adjacent memory locations, potentially leading to code execution with the privileges of the affected application process. The vulnerability demonstrates how seemingly innocuous components like font rendering can become critical attack vectors when memory safety is not properly enforced.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to include potential privilege escalation and arbitrary code execution capabilities. When exploited successfully, attackers can gain control over the Windows operating system running either VMware Workstation or Horizon View Client, potentially allowing them to install malware, modify system files, or establish persistent access to the compromised environment. The vulnerability affects both guest operating systems within VMware Workstation and the host Windows systems running the Horizon View Client, creating a multi-layered threat that can propagate through virtualized environments. Organizations using these VMware products without proper patch management or security controls are particularly vulnerable, as the default configuration settings make exploitation more likely in Horizon View deployments. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation, demonstrating how font processing can be weaponized for broader attack objectives.
Mitigation strategies should focus on immediate patch deployment to address the vulnerability in affected VMware products, ensuring that all systems are updated to versions 12.5.3 or later for Workstation and 4.4.0 or later for Horizon View Client. Organizations should also consider disabling virtual printing functionality when it is not required, particularly in Horizon View environments where this feature is enabled by default. Network segmentation and access controls should be implemented to limit the potential impact of successful exploitation attempts. Security monitoring should include detection of unusual font processing activities and potential buffer overflow indicators within virtualized environments. Additionally, regular vulnerability assessments and penetration testing should be conducted to identify similar issues in other VMware components or third-party applications that may be similarly vulnerable to heap-based buffer overflow conditions. The vulnerability serves as a reminder of the importance of memory safety in widely deployed software components and the need for comprehensive security testing throughout the software development lifecycle.