CVE-2026-85912 in Windows
Summary
by MITRE • 10/14/2026
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Clipboard User Service allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified involves a race condition within the Windows Clipboard User Service, specifically arising from concurrent access to shared resources without proper synchronization mechanisms. This flaw represents a classic instance of CWE-362, which categorizes issues related to concurrent execution using shared resources with improper synchronization. In this context, multiple threads or processes may attempt to read and write data simultaneously, creating a window where the state of the system can be manipulated before it is properly secured by locks or atomic operations. The absence of robust locking protocols allows an attacker to exploit timing discrepancies in how the service handles clipboard data, leading to unpredictable behavior that deviates from the intended security model.
An authorized local attacker who has already gained a foothold on the system can leverage this race condition to escalate privileges beyond their current user context. By carefully crafting requests and manipulating the timing of operations against the Clipboard User Service, the attacker can force the service into an inconsistent state or bypass access controls that are designed to restrict certain actions to higher-privileged accounts. This exploitation path aligns with ATT&CK technique T1068, which covers Exploitation for Privilege Escalation, as it involves leveraging specific software vulnerabilities rather than misconfigurations or weak credentials. The attacker does not need to exploit a buffer overflow or injection flaw but instead relies on the logical error in how concurrent operations are serialized and validated by the operating system component.
The operational impact of this vulnerability is significant because it undermines the integrity of local privilege boundaries within Windows environments. Once an attacker successfully exploits this race condition, they may gain access to sensitive data stored in the clipboard or execute code with elevated permissions, potentially leading to full control over the affected host. This can result in unauthorized modification of system configurations, installation of persistent backdoors, or lateral movement across a network if the compromised account possesses broader administrative rights. The severity is further compounded by the fact that the Clipboard User Service runs as part of the user session infrastructure, meaning it is frequently active and accessible to any application running under the logged-in user’s context, thereby increasing the attack surface for local exploitation attempts.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. Microsoft has addressed this issue through security updates that patch the underlying synchronization logic within the Clipboard User Service, ensuring that shared resources are accessed atomically or protected by appropriate mutexes to prevent race conditions. Administrators must ensure that all systems running affected versions of Windows have received these critical patches as soon as possible. In addition to applying vendor-supplied fixes, organizations should enforce strict least-privilege principles for user accounts and applications interacting with clipboard services. Implementing application control policies can also restrict the execution of untrusted software that might attempt to exploit such timing vulnerabilities. Regular auditing of system logs for unusual activity patterns associated with privilege escalation attempts will aid in detecting potential exploitation efforts before they result in a full compromise.