CVE-2019-0786 in Windows
Summary
by MITRE
An elevation of privilege vulnerability exists in the Microsoft Server Message Block (SMB) Server when an attacker with valid credentials attempts to open a specially crafted file over the SMB protocol on the same machine, aka 'SMB Server Elevation of Privilege Vulnerability'.
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Analysis
by VulDB Data Team • 08/27/2023
The vulnerability identified as CVE-2019-0786 represents a critical elevation of privilege flaw within Microsoft's Server Message Block protocol implementation. This security weakness specifically affects the SMB Server component and exploits a fundamental flaw in how the system handles file operations over the SMB protocol. The vulnerability requires an attacker to possess valid credentials to the target system, making it less accessible than fully remote exploits but still highly concerning given the potential for privilege escalation. The flaw manifests when an authenticated user attempts to open a specially crafted file through the SMB protocol on the same machine where the server is running, creating a scenario where legitimate system access can be leveraged to gain higher privileges.
The technical nature of this vulnerability stems from improper validation of file operations within the SMB server implementation. When a user with valid credentials attempts to open a maliciously crafted file through SMB, the system fails to properly sanitize or validate the file handle operations, allowing an attacker to manipulate the underlying system resources. This flaw falls under the CWE-119 category of "Improper Access to Resource Through Symbolic Link" and aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation." The vulnerability essentially creates a path where legitimate authentication can be abused to bypass normal privilege boundaries within the SMB subsystem, allowing a user to execute code with elevated privileges that should normally be restricted.
The operational impact of CVE-2019-0786 extends beyond simple privilege escalation as it can enable attackers to gain system-level control over affected systems. Once successfully exploited, an attacker can potentially access sensitive system files, modify critical configurations, establish persistence mechanisms, and move laterally within a network environment. The vulnerability affects multiple versions of Windows operating systems including Windows 10, Windows Server 2016, and Windows Server 2019, making it particularly dangerous in enterprise environments where these systems are commonly deployed. The attack vector requires local access or network connectivity to the target system, but the privilege escalation potential means that even limited access can be leveraged to achieve significant system compromise.
Microsoft addressed this vulnerability through security updates released in their regular patching cycle, specifically in the May 2019 security updates. Organizations should implement the corresponding security patches immediately to mitigate the risk. Additional mitigations include restricting SMB access where possible, implementing network segmentation to limit potential attack vectors, and monitoring for suspicious file access patterns. The vulnerability demonstrates the importance of proper input validation and resource management within network protocols, particularly those handling file operations and system-level access. Security professionals should also consider implementing endpoint detection and response solutions that can identify anomalous file access patterns that may indicate exploitation attempts. The flaw serves as a reminder of the critical need for thorough security testing of protocol implementations and the potential for authenticated users to be leveraged as attack vectors in privilege escalation scenarios.