CVE-2026-85938 in Windows
Summary
by MITRE • 10/14/2026
Improper access control in Windows Broadcast DVR 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 within the Windows Broadcast DVR User Service represents a critical failure in implementing proper access controls, specifically categorized under CWE-269: Improper Privilege Management or CWE-732: Incorrect Permission Assignment for Critical Resource depending on the specific implementation details of the service. This flaw allows an authorized attacker to disclose sensitive information locally by exploiting insufficient restrictions on resource access. The Broadcast DVR User Service is a core component of the Windows operating system responsible for managing digital video recording and broadcasting functionalities, including support for TV tuners and media center features. While this service operates with specific privileges necessary for its function, the improper configuration or coding error within it creates an avenue where users who already possess valid authentication credentials can escalate their access beyond intended boundaries to retrieve restricted data.
From a technical perspective, the root cause lies in the misconfiguration of security descriptors associated with the IPC endpoints or file system objects managed by the service. When an application requests interaction with this service, the operating system checks the caller's token against the defined discretionary access control list (DACL). In this vulnerable scenario, these DACLs are either too permissive or fail to properly validate the context of the request, allowing a local user to invoke methods that return internal state information, configuration details, or potentially cached media data intended for higher-privileged processes. This is not an elevation of privilege in the sense of gaining SYSTEM rights, but rather an unauthorized disclosure of information that should remain isolated from standard user contexts. The attacker leverages this flaw by crafting specific API calls to the service interface, bypassing logical checks that would normally restrict such queries based on the caller's role or session type.
The operational impact of this vulnerability is primarily centered around confidentiality loss within a local environment. An authenticated adversary can exploit this weakness to gather intelligence about the system configuration, potentially identifying installed media components, network settings related to broadcasting, or other sensitive metadata stored by the service. While the immediate risk may seem limited compared to remote code execution vulnerabilities, it serves as a significant stepping stone in an attack chain. The disclosed information can be used for further reconnaissance, aiding in the identification of additional targets within the local network or facilitating social engineering attacks based on detailed system profiling. Furthermore, if the exposed data includes cryptographic keys or session tokens associated with media streaming services, the confidentiality of ongoing communications could also be compromised.
In alignment with industry standards, this vulnerability maps to MITRE ATT&CK technique T1083: File and Directory Discovery, as the attacker is actively probing for accessible files and directories through service interactions. It also relates to T1528: Steal Application Access Token if the disclosed information includes tokens that can be hijacked. The lack of strict separation between privileged operations and user-accessible interfaces highlights a common pattern in legacy Windows services where backward compatibility or ease of development overrides security best practices. To mitigate this risk, Microsoft has released patches that correct the access control lists associated with the Broadcast DVR User Service endpoints. Administrators should ensure that all systems are updated to the latest cumulative updates containing these fixes. Additionally, implementing principle of least privilege at the application level and monitoring for unusual API calls to system services can help detect exploitation attempts in real-time. Regular auditing of service permissions using tools like Sysinternals AccessChk is recommended to verify that no excessive rights have been inadvertently assigned during configuration changes or software installations.