CVE-2020-3948 in Workstation
Summary
by MITRE
Linux Guest VMs running on VMware Workstation (15.x before 15.5.2) and Fusion (11.x before 11.5.2) contain a local privilege escalation vulnerability due to improper file permissions in Cortado Thinprint. Local attackers with non-administrative access to a Linux guest VM with virtual printing enabled may exploit this issue to elevate their privileges to root on the same guest VM.
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Analysis
by VulDB Data Team • 03/17/2020
The vulnerability identified as CVE-2020-3948 represents a critical local privilege escalation flaw affecting Linux guest virtual machines operating on VMware Workstation and Fusion platforms. This security issue stems from improper file permissions within the Cortado Thinprint component, which is utilized for virtual printing functionality in these virtualized environments. The vulnerability specifically impacts versions 15.x prior to 15.5.2 for Workstation and 11.x prior to 11.5.2 for Fusion, creating a persistent security risk for users who have access to a Linux guest VM with virtual printing enabled. The flaw allows attackers with standard user privileges to escalate their access level to root privileges, fundamentally compromising the security boundary of the virtual machine.
The technical root cause of this vulnerability lies in the inadequate permission settings applied to specific files within the Cortado Thinprint implementation. These improperly configured file permissions create a path for privilege escalation where a local attacker can manipulate system resources to gain elevated privileges. The vulnerability is classified as a local privilege escalation issue, meaning it requires physical or logical access to the target system but does not necessitate network-based exploitation. The flaw operates through a combination of file system misconfigurations and privilege handling mechanisms that fail to properly enforce access controls, allowing unauthorized users to bypass normal security boundaries. This type of vulnerability aligns with CWE-276, which specifically addresses improper file permissions, and represents a classic example of inadequate access control implementation in virtualized environments.
The operational impact of CVE-2020-3948 extends beyond simple privilege escalation, as it fundamentally undermines the security model of virtualized computing environments. When exploited successfully, this vulnerability enables attackers to gain root access to the Linux guest VM, providing them with complete control over the system's resources, files, and processes. The implications are particularly severe in multi-user environments where virtual machines serve as isolated computing domains, as this vulnerability allows for complete compromise of the guest operating system. Attackers can leverage this privilege escalation to install persistent backdoors, exfiltrate sensitive data, modify system configurations, or establish covert communication channels. The vulnerability also affects the trust model inherent in virtualization, as it allows for unauthorized access to resources that should be protected from non-administrative users, potentially enabling further attacks on the host system or other guest VMs in the same environment.
Mitigation strategies for CVE-2020-3948 primarily focus on updating affected VMware products to versions that address the improper file permissions in Cortado Thinprint. System administrators should immediately upgrade VMware Workstation to version 15.5.2 or later and VMware Fusion to version 11.5.2 or later to resolve the vulnerability. Additionally, organizations should consider disabling virtual printing functionality in guest VMs when it is not required, as this reduces the attack surface for exploitation. Security monitoring should be enhanced to detect unusual privilege escalation attempts or unauthorized file access patterns within virtual machine environments. The vulnerability also highlights the importance of proper access control implementation in virtualized environments, reinforcing principles from the MITRE ATT&CK framework that emphasize the need for robust privilege management and access control mechanisms. Organizations should implement regular security assessments of their virtualized environments to identify and remediate similar permission-related vulnerabilities that could compromise system integrity and security boundaries.