CVE-2019-1289 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists when the Windows Update Delivery Optimization does not properly enforce file share permissions, aka 'Windows Update Delivery Optimization Elevation of Privilege Vulnerability'.
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Analysis
by VulDB Data Team • 08/20/2020
The Windows Update Delivery Optimization feature represents a critical elevation of privilege vulnerability that stems from improper enforcement of file share permissions within the Windows operating system. This vulnerability specifically affects the mechanism by which Windows Update delivers content to local networks, where the system fails to adequately validate access controls when managing shared files used for peer-to-peer distribution of updates. The flaw exists in the way the delivery optimization service handles file permissions, creating a pathway for unauthorized users to gain elevated system privileges through manipulation of shared update files.
From a technical perspective, the vulnerability manifests when the Windows Update Delivery Optimization component creates and manages shared folders containing update content without proper access control validation. The system's permission model fails to enforce appropriate restrictions on file shares, allowing local users to potentially access and modify files that should be restricted to system-level operations. This misconfiguration enables attackers to exploit the service by creating malicious files within shared directories or by manipulating existing shared update content to execute arbitrary code with elevated privileges. The vulnerability operates at the system level where standard user accounts can potentially escalate their privileges to administrator level through manipulation of the update sharing mechanisms.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it affects the fundamental security model of Windows Update functionality. Attackers can leverage this flaw to bypass standard security controls that typically prevent local users from accessing privileged system resources. The vulnerability affects systems running various Windows versions including windows 10, windows server 2016, and windows server 2019, where the delivery optimization feature is enabled by default or configured to operate in peer-to-peer sharing modes. This creates a widespread risk across enterprise environments where Windows Update Delivery Optimization is commonly deployed to reduce bandwidth consumption and improve update distribution efficiency.
Security researchers have classified this vulnerability according to CWE-276, which addresses improper permissions and access control issues within software systems. The vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and represents a classic path for attackers to move from user-level access to administrative privileges. Organizations utilizing Windows Update Delivery Optimization in their deployment strategies face significant risk from this vulnerability, as it allows attackers to potentially compromise entire networks through a single compromised endpoint. The attack vector typically involves local user exploitation where an attacker with basic user access can manipulate shared file permissions to execute malicious code with elevated privileges.
Mitigation strategies for this vulnerability primarily focus on disabling or properly configuring the Windows Update Delivery Optimization feature. Organizations should consider implementing Group Policy settings to disable peer-to-peer sharing of updates or restrict the feature to specific network environments where proper access controls are in place. Security teams should also implement monitoring for unusual file share activities and ensure that proper network segmentation prevents unauthorized access to shared update directories. Microsoft has released patches addressing this vulnerability through regular security updates, and organizations must ensure timely deployment of these patches to eliminate the risk. Additionally, network administrators should review and harden file share permissions for all Windows update-related directories, implementing principle of least privilege access controls to prevent unauthorized modification of shared update content.