CVE-2017-8625 in Internet Explorer
Summary
by MITRE
Internet Explorer in Windows 10 Gold, 1511, 1607, 1703, and Windows Server 2016 allows an attacker to bypass Device Guard User Mode Code Integrity (UCMI) policies due to Internet Explorer failing to validate UMCI policies, aka "Internet Explorer Security Feature Bypass Vulnerability".
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Analysis
by VulDB Data Team • 01/07/2021
The CVE-2017-8625 vulnerability represents a critical security flaw in Microsoft Internet Explorer that undermines fundamental operating system security mechanisms. This vulnerability specifically affects Windows 10 versions 1511, 1607, 1703, and Windows Server 2016, where Internet Explorer fails to properly validate User Mode Code Integrity policies. The flaw enables attackers to bypass Device Guard protections that are designed to prevent unauthorized code execution in user mode contexts. Device Guard is a security feature that enforces code integrity policies to ensure only trusted software can run in user mode, creating a critical defense barrier against malicious code injection and privilege escalation attacks.
The technical root cause of this vulnerability lies in Internet Explorer's insufficient validation of UMCI policies during the execution of web content. When Internet Explorer processes web pages, it should verify that the code being executed complies with the Device Guard policies that have been configured by administrators. However, the vulnerability allows malicious code to circumvent these checks, effectively disabling the code integrity protections that should be enforced by the operating system. This failure occurs at the kernel-level validation mechanisms where UMCI policies are supposed to be enforced, creating a pathway for attackers to execute arbitrary code that would normally be blocked by the security framework.
The operational impact of this vulnerability is severe and far-reaching within enterprise environments that rely on Device Guard for protection against advanced persistent threats. Attackers can leverage this vulnerability to bypass security controls that are typically effective against zero-day exploits and targeted attacks. The bypass allows for the execution of malicious code that can escalate privileges, access sensitive data, and potentially establish persistent backdoors within the system. This vulnerability particularly affects organizations that have implemented strict Device Guard policies as part of their security posture, since the flaw undermines the very foundation of these protective measures. The attack surface is broad as Internet Explorer is commonly used across organizations, making this vulnerability particularly dangerous in corporate environments where security policies are strictly enforced.
Mitigation strategies for CVE-2017-8625 should focus on immediate patching of affected systems and implementation of additional security controls. Microsoft released security updates that address this vulnerability by fixing the UMCI policy validation mechanism within Internet Explorer. Organizations should prioritize deployment of these patches across all affected Windows 10 and Windows Server 2016 systems. In addition to patching, administrators should consider implementing additional security measures such as disabling Internet Explorer or using alternative browsers for sensitive operations. The vulnerability aligns with CWE-119, which describes weaknesses in memory handling that can lead to security bypasses, and maps to ATT&CK techniques related to privilege escalation and code injection. Organizations should also review their Device Guard policies to ensure they are properly configured and monitor for suspicious activities that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and the potential consequences of failing to address browser-based security flaws that can compromise entire operating system protection mechanisms.