CVE-2026-92374 in Full Client
Summary
by MITRE • 10/27/2026
A time-of-check time-of-use (TOCTOU) race condition combined with improper symbolic link handling in the privileged helper of TeamViewer Full Client and Host prior to version 15.83 for macOS allows a local attacker with low privileges to bypass installer package verification and install a malicious package. Successful exploitation can lead to local privilege escalation to root.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability described represents a critical security flaw within the privileged helper component of TeamViewer Full Client and Host software on macOS, specifically affecting versions prior to 15.83. This issue stems from a classic time-of-check time-of-use race condition coupled with improper handling of symbolic links during the installation process. In this context, the installer package verification mechanism fails to maintain atomicity between checking the integrity or authenticity of an installer and subsequently executing it. An attacker operating under low-privilege user accounts can exploit this temporal gap by manipulating file system states, specifically through the creation and manipulation of symbolic links, to redirect the installation process toward malicious payloads rather than legitimate software components.
From a technical perspective, the core flaw lies in how the privileged helper interacts with the macOS file system during package verification. The application likely performs an initial check on a target path or file to ensure it is safe before proceeding with installation. However, due to the race condition, there exists a window of opportunity where the state of that path can be altered between the moment of verification and the moment of use. By leveraging symbolic links, which are essentially pointers to other files or directories in Unix-like systems including macOS, an attacker can substitute the expected legitimate file with a malicious one during this narrow interval. This allows the privileged helper to inadvertently process and execute code that has not been properly verified by the intended security controls.
The operational impact of successfully exploiting this vulnerability is severe, resulting in local privilege escalation from a standard user account to root-level access on the affected macOS system. Once an attacker gains root privileges, they effectively compromise the entire operating environment. This level of access allows for unrestricted reading and writing of sensitive data, installation of persistent backdoors, modification of system configurations, and potential lateral movement within connected networks if the machine is part of a larger infrastructure. The ability to bypass installer package verification undermines one of the primary defense mechanisms against unauthorized software execution on macOS systems, which rely heavily on code signing and integrity checks for security assurance.
This vulnerability aligns with several well-known industry standards regarding common weaknesses in computing. It corresponds directly to CWE-367, Time-of-check time-of-use race condition, as it involves a failure to maintain consistent state between checking and using resources. Additionally, the improper handling of symbolic links maps closely to CWE-59 Improper Link Resolution Before File Access or symlink following vulnerabilities. In terms of offensive security frameworks such as MITRE ATT&CK, this exploitation technique relates to techniques involving privilege escalation via local exploits, specifically those that abuse system configuration or installer mechanisms. The use of symbolic links for redirection is a common tactic in bypassing access controls and integrity checks on Unix-based systems.
To mitigate the risks associated with this vulnerability, organizations must prioritize immediate patching by upgrading TeamViewer Full Client and Host to version 15.83 or later where these issues have been addressed. Until patches are applied, administrators should enforce strict file system permissions and monitor for unusual symbolic link creations in directories used by the installer helper processes. Implementing mandatory access control policies such as macOS System Integrity Protection can also help restrict unauthorized modifications to critical system areas. Furthermore, deploying endpoint detection and response solutions that flag anomalous privilege escalation attempts or unexpected changes to installed applications can provide an additional layer of defense against exploitation of this race condition. Regular auditing of installer logs and monitoring for deviations in expected installation behaviors are recommended operational security practices to detect potential abuse of this flaw before significant damage occurs.