CVE-2020-8871 in Parallels Desktop
Summary
by MITRE
This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop 15.1.0-47107 . An attacker must first obtain the ability to execute high-privileged code on the target guest system in order to exploit this vulnerability. The specific flaw exists within the VGA virtual device. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can leverage this vulnerability to escalate privileges and execute code in the context of the hypervisor. Was ZDI-CAN-9403.
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Analysis
by VulDB Data Team • 05/11/2024
The vulnerability described in CVE-2020-8871 represents a critical privilege escalation flaw within Parallels Desktop version 15.1.0-47107 that specifically targets the VGA virtual device implementation. This issue demonstrates a classic buffer overflow vulnerability that occurs when the virtualized graphics subsystem fails to properly validate input data supplied by guest operating systems. The vulnerability exists at the hypervisor level where guest systems can potentially exploit this flaw to gain elevated privileges and execute arbitrary code with the same privileges as the hypervisor itself. The attack requires an initial foothold within the guest system where an attacker can execute high-privileged code, making this a sophisticated exploit that operates within the confines of a virtualized environment.
The technical nature of this vulnerability stems from improper input validation within the VGA virtual device driver, which is classified under CWE-121 as a "Stack-based Buffer Overflow" or potentially CWE-787 for "Out-of-bounds Write." The flaw manifests when user-supplied data is processed without adequate bounds checking, allowing an attacker to write data beyond the allocated buffer space. This type of vulnerability is particularly dangerous in virtualization environments because it can be leveraged to break out of the guest operating system boundaries and gain access to the underlying hypervisor. The attack vector specifically targets the graphics processing subsystem where guest operating systems interact with virtualized hardware components, making it a sophisticated exploitation target that requires understanding of both virtualization internals and graphics driver behavior.
From an operational impact perspective, this vulnerability poses significant risk to organizations relying on Parallels Desktop for virtualization services. The privilege escalation capability means that an attacker who successfully exploits this vulnerability can execute code with the highest privileges available to the hypervisor, potentially allowing complete system compromise. This could result in data theft, persistence mechanisms being established, or further lateral movement within network environments. The vulnerability's location within the VGA device driver makes it particularly challenging to detect and mitigate, as it operates at a low level within the virtualization stack. The fact that this issue was tracked by ZDI-CAN-9403 indicates it was recognized by the cybersecurity community as a serious concern affecting virtualization platforms and their security boundaries.
Mitigation strategies for CVE-2020-8871 should focus on both immediate patching and operational security measures. Organizations must prioritize updating to the latest version of Parallels Desktop that contains the necessary security fixes, as this vulnerability specifically affects version 15.1.0-47107 and earlier releases. Network segmentation and access controls should be implemented to limit the potential attack surface where guest systems can execute code with elevated privileges. Monitoring for anomalous behavior within virtualized environments, particularly around graphics processing and memory allocation patterns, should be enhanced. From an ATT&CK framework perspective, this vulnerability relates to T1055 for Process Injection and T1068 for Exploitation for Privilege Escalation, making it important for security teams to monitor for these techniques in virtualized environments. Additionally, implementing hypervisor-level security controls and ensuring that guest operating systems maintain strict privilege boundaries can help prevent exploitation of such vulnerabilities.