CVE-2011-4434 in Windows
Summary
by MITRE
Microsoft Windows Server 2008 R2 and R2 SP1 and Windows 7 Gold and SP1 do not properly enforce AppLocker rules, which allows local users to bypass intended access restrictions via a (1) macro or (2) scripting feature in an application, as demonstrated by Microsoft Office applications and the SANDBOX_INERT and LOAD_IGNORE_CODE_AUTHZ_LEVEL flags.
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Analysis
by VulDB Data Team • 11/26/2021
Microsoft Windows Server 2008 R2 and Windows 7 systems contain a critical flaw in their AppLocker implementation that undermines the security controls designed to restrict application execution. This vulnerability resides in the operating system's application control framework where AppLocker policies are meant to enforce access restrictions by controlling which applications can run on a system. The flaw specifically affects how the system handles macro execution and scripting features within applications, creating a bypass mechanism that allows local attackers to circumvent intended security controls.
The technical implementation of this vulnerability stems from improper enforcement of AppLocker rules when processing application features that utilize macro capabilities or scripting functions. Attackers can exploit this weakness by leveraging Microsoft Office applications which contain built-in macro execution capabilities and scripting features. The exploitation occurs when the system fails to properly validate or enforce AppLocker policies during the execution of these features, particularly when the SANDBOX_INERT and LOAD_IGNORE_CODE_AUTHZ_LEVEL flags are utilized. These flags effectively disable certain code authorization checks, allowing malicious code to execute outside the intended security boundaries established by AppLocker policies.
The operational impact of this vulnerability is significant as it provides local users with the ability to bypass application control measures that are critical for maintaining system integrity and preventing unauthorized software execution. This weakness essentially renders AppLocker policies ineffective for certain types of applications, particularly those that support macro functionality or scripting capabilities. The vulnerability affects both Windows Server 2008 R2 and Windows 7 systems, creating a widespread security concern across enterprise environments where application control is essential for mitigating attack surface and preventing the execution of malicious software. This flaw particularly impacts organizations that rely on AppLocker as part of their security strategy for preventing unauthorized application execution and maintaining compliance with security policies.
Organizations should implement immediate mitigations including applying the relevant Microsoft security updates that address this AppLocker bypass vulnerability. System administrators should also consider implementing additional security controls such as disabling macro execution in Office applications where possible, implementing stricter group policy configurations, and monitoring for suspicious application execution patterns. The vulnerability aligns with CWE-693, which addresses protection mechanism failures, and represents a specific implementation weakness in the application control framework. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and persistence through application control bypass, potentially enabling attackers to establish more persistent access within compromised systems. Organizations should also consider deploying endpoint detection and response solutions to monitor for exploitation attempts and maintain visibility into application execution patterns that may indicate attempted bypass of security controls.