CVE-2021-22000 in Thinapp
Summary
by MITRE • 07/13/2021
VMware Thinapp version 5.x prior to 5.2.10 contain a DLL hijacking vulnerability due to insecure loading of DLLs. A malicious actor with non-administrative privileges may exploit this vulnerability to elevate privileges to administrator level on the Windows operating system having VMware ThinApp installed on it.
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Analysis
by VulDB Data Team • 07/18/2021
The vulnerability identified as CVE-2021-22000 represents a critical privilege escalation flaw in VMware ThinApp versions 5.x prior to 5.2.10, specifically manifesting as a DLL hijacking vulnerability. This weakness arises from the insecure loading of dynamic link library files within the application's execution environment, creating a pathway for unauthorized privilege elevation. The vulnerability is particularly concerning because it allows attackers with standard user privileges to escalate their access level to administrator status on Windows systems where VMware ThinApp is installed.
The technical flaw stems from improper DLL search order handling within the VMware ThinApp application, which follows a predictable and insecure sequence when resolving dynamic library dependencies. When the application attempts to load required DLLs, it first searches in the current working directory before checking system directories, creating an opportunity for malicious actors to place specially crafted DLL files in the application's directory. This behavior aligns with CWE-426, which describes insecure search paths that allow attackers to inject malicious code through the system's library loading mechanism. The vulnerability operates under the principle that applications should not trust the current working directory when loading DLLs without explicit verification of their source and integrity.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally undermines the security model of Windows systems running VMware ThinApp. Attackers can exploit this weakness by placing malicious DLL files in strategic locations where they will be loaded by the vulnerable application, effectively bypassing standard user access controls. This presents a significant risk to enterprise environments where VMware ThinApp is widely deployed for application virtualization and packaging, as it provides a persistent mechanism for attackers to gain administrative access. The vulnerability affects systems with multiple user accounts and shared resources, making it particularly dangerous in multi-user environments where standard security boundaries may be compromised.
Mitigation strategies for CVE-2021-22000 should prioritize immediate patch deployment to VMware ThinApp version 5.2.10 or later, which addresses the insecure DLL loading behavior through proper search order implementation and enhanced library validation. Organizations should also implement additional security controls including application whitelisting policies that restrict which DLLs can be loaded by the ThinApp application, regular monitoring of the application's working directory for unauthorized DLL files, and network segmentation to limit access to systems running vulnerable versions. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the T1068 - Exploitation for Privilege Escalation tactic, and organizations should consider implementing defensive measures such as process monitoring, file integrity checking, and enhanced logging to detect potential exploitation attempts. Security teams should also conduct comprehensive vulnerability assessments to identify all systems running affected VMware ThinApp versions and establish incident response procedures specifically designed to handle such privilege escalation scenarios.