CVE-2026-85866 in Windows
Summary
by MITRE • 10/14/2026
Exposure of sensitive system information to an unauthorized control sphere in Windows ALPC allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves a flaw within the Local Procedure Call (ALPC) mechanism in Microsoft Windows, which is designed to facilitate secure communication between processes on the same machine. Specifically, this issue stems from improper handling of access control checks when managing sensitive system information through ALPC endpoints. While ALPC generally enforces strict security boundaries to prevent unauthorized cross-process data exchange, a specific logic error or misconfiguration allows an attacker who has already gained authorized local execution privileges to bypass these intended restrictions. This flaw effectively creates a pathway for the disclosure of privileged system data that should remain isolated from lower-privileged contexts, thereby violating the principle of least privilege and compartmentalization within the operating system architecture.
From a technical perspective, ALPC serves as the primary inter-process communication (IPC) mechanism in modern Windows versions, replacing older methods like RPC for local calls due to its efficiency and security features. The vulnerability likely arises from an inconsistency in how token privileges or integrity levels are validated during specific IPC operations. An attacker leveraging this flaw can exploit the misconfigured access control logic to read memory regions, kernel structures, or other sensitive data that are normally protected by higher integrity level requirements. This is not a remote code execution vector but rather a local privilege escalation or information disclosure vulnerability, where the initial foothold requires some form of authenticated user context on the target system.
The operational impact of this vulnerability centers on the potential for lateral movement and deeper reconnaissance within an infected network. By disclosing sensitive system information, such as security tokens, kernel pointers, or configuration data, an attacker can gather critical intelligence needed to escalate privileges further or bypass additional security controls like User Account Control (UAC) or Data Execution Prevention (DEP). This exposure undermines the integrity of the local security boundary, allowing malicious actors to map out the system environment with greater accuracy than previously possible. In enterprise environments, this could facilitate attacks against domain controllers or other high-value assets if the compromised host is used as a pivot point for further exploitation.
This issue aligns closely with CWE-200, which categorizes information exposure vulnerabilities where sensitive data becomes available to unauthorized actors. It also relates to ATT&CK technique T1083, File and Directory Discovery, although in this context, the discovery extends beyond standard files to include system-level structures accessible via IPC mechanisms. The vulnerability highlights the complexity of maintaining robust access controls within complex subsystems like ALPC, where subtle logic errors can have significant security implications despite the overall strength of the Windows security model.
Mitigation strategies primarily involve applying the latest cumulative updates provided by Microsoft, which address these specific flaws in the ALPC implementation system-wide. Organizations should ensure that all endpoints are patched promptly to close this information disclosure vector. Additionally, implementing strict application whitelisting and monitoring for unusual IPC activity can help detect exploitation attempts early. Security teams should also enforce strong access control policies and limit local administrative privileges wherever possible to reduce the attack surface available to potential adversaries who might attempt to leverage such vulnerabilities for initial foothold establishment or privilege escalation.