CVE-2021-34869 in Parallels
Summary
by MITRE • 01/25/2022
This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop 16.1.3-49160. An attacker must first obtain the ability to execute low-privileged code on the target guest system in order to exploit this vulnerability. The specific flaw exists within the Toolgate component. The issue results from the lack of proper validation of user-supplied data, which can result in an uncontrolled memory allocation. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the hypervisor. Was ZDI-CAN-13797.
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Analysis
by VulDB Data Team • 01/28/2022
The vulnerability identified as CVE-2021-34869 represents a critical privilege escalation flaw within Parallels Desktop version 16.1.3-49160 that enables local attackers to gain elevated system privileges and execute arbitrary code within the hypervisor context. This vulnerability specifically affects the Toolgate component, which serves as a communication interface between guest operating systems and the hypervisor environment. The flaw stems from inadequate input validation mechanisms that fail to properly sanitize user-supplied data before processing, creating a pathway for malicious exploitation. Security researchers have classified this issue under CWE-122, which encompasses improper restriction of operations within a limited context, and it aligns with ATT&CK technique T1068, which describes privilege escalation through local exploitation of software vulnerabilities. The vulnerability requires an attacker to first establish a foothold within the guest system through low-privileged code execution, but once achieved, the flaw provides a direct route to hypervisor-level access.
The technical implementation of this vulnerability centers on uncontrolled memory allocation within the Toolgate component's data processing pipeline. When user-supplied data is passed through this interface without proper validation, the system allocates memory buffers based on attacker-controlled parameters, leading to potential memory corruption and arbitrary code execution. This memory allocation flaw allows an attacker to manipulate the heap or stack structures in ways that can bypass normal privilege boundaries. The vulnerability specifically targets the hypervisor's privilege escalation mechanisms, where guest operating system processes can leverage the flawed Toolgate component to execute code with elevated privileges that match those of the hypervisor itself. This creates a severe security risk because the hypervisor typically operates with the highest privilege level on the host system, making successful exploitation equivalent to gaining complete system control.
The operational impact of CVE-2021-34869 extends beyond simple privilege escalation, as it fundamentally compromises the isolation guarantees that virtualization environments are designed to provide. An attacker who successfully exploits this vulnerability can execute arbitrary code within the hypervisor context, potentially allowing them to access all virtual machines running on the same host, extract sensitive data from other guests, modify virtual disk images, or even establish persistent backdoors. This vulnerability undermines the core security model of virtualization by enabling attackers to break out of their designated guest environments and gain control over the entire host system. The implications are particularly severe in enterprise environments where multiple virtual machines may be running on a single host, as exploitation could potentially compromise the entire virtual infrastructure. Organizations using Parallels Desktop in security-sensitive environments face significant risk from this vulnerability, as it provides a direct pathway for attackers to bypass traditional security controls and gain access to sensitive corporate data.
Mitigation strategies for CVE-2021-34869 should prioritize immediate patching of affected Parallels Desktop installations to the latest available versions that address the Toolgate component vulnerability. Organizations should implement network segmentation and access controls to limit the potential attack surface, particularly by restricting guest system access to privileged operations. Security monitoring should focus on detecting anomalous memory allocation patterns and unexpected privilege escalation events within virtualized environments. System administrators should consider implementing additional security controls such as hypervisor hardening measures, regular security assessments of virtual environments, and enhanced logging of hypervisor-level activities. Organizations should also review their virtualization security policies to ensure proper isolation between guest operating systems and implement least-privilege principles for all virtual machine configurations. The vulnerability demonstrates the importance of validating all user-supplied input within hypervisor components and highlights the need for comprehensive security testing of virtualization infrastructure to prevent similar issues in the future.