CVE-2026-83893 in Windows
Summary
by MITRE • 10/14/2026
Exposure of sensitive system information to an unauthorized control sphere in Windows Clipboard User Service allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified involves a flaw within the Windows Clipboard User Service, specifically concerning how it handles and exposes sensitive system information to processes that lack appropriate authorization levels. This issue stems from improper access controls or insufficient isolation mechanisms inherent in the service's architecture, allowing an attacker who has already gained local execution privileges on the target system to interact with the clipboard subsystem in ways intended for trusted applications only. The core technical flaw lies in the failure of the Clipboard User Service to strictly enforce security boundaries between different user contexts and application privilege levels when managing data stored in or retrieved from the clipboard buffer. This misconfiguration effectively creates a side-channel through which confidential data, such as copied text containing passwords, personal identification numbers, financial details, or proprietary code snippets, can be intercepted by malicious software running under lower privileges than those required for normal clipboard operations.
From an operational perspective, this vulnerability enables local information disclosure attacks where the threat actor leverages their existing foothold on the system to harvest sensitive data without needing elevated administrative rights initially. The impact is particularly severe in environments where users frequently copy and paste sensitive credentials or confidential documents between applications with varying trust levels. An attacker can craft a malicious application that hooks into clipboard events or queries the clipboard state at precise intervals, capturing any sensitive content pasted by the user before it reaches its intended destination. This capability facilitates further lateral movement within an enterprise network if the disclosed information includes domain credentials or internal system configurations, thereby escalating the risk from simple data theft to potential full system compromise and persistent access establishment.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-200: Exposure of Sensitive Information to an Unauthorized Actor, as it involves the unintended leakage of private data due to inadequate security controls. Additionally, in terms of tactical execution within the MITRE ATT&CK framework, this flaw supports techniques related to Credential Access via Input Capture or Data from Local System, specifically under sub-techniques that involve intercepting clipboard content for subsequent exfiltration or analysis. The attack vector is classified as local, requiring physical access or prior code execution on the target machine, which places it within the context of post-exploitation activities rather than remote exploitation scenarios.
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 service logic to enforce stricter permission checks before allowing clipboard data access by untrusted processes. Organizations must ensure that all Windows systems are updated with the latest cumulative patches released for their respective operating system versions, as these updates contain the necessary fixes to restrict unauthorized access to sensitive clipboard contents. Beyond patching, administrators should implement application control policies using tools like Microsoft AppLocker or Windows Defender Application Control to prevent untrusted applications from executing on endpoints where high-value data is processed. Furthermore, user education regarding safe clipboard practices, such as avoiding copying credentials directly into web forms and utilizing password managers with secure copy mechanisms that bypass standard system clipboards when possible, can reduce the attack surface available to local threats. Regular auditing of running processes and monitoring for unusual clipboard activity patterns using endpoint detection and response solutions can also aid in early identification of exploitation attempts targeting this weakness.