CVE-2017-8723 in Edge
Summary
by MITRE
Microsoft Edge in Microsoft Windows 10 Gold, 1511, 1607, 1703, and Windows Server 2016 allows an attacker to trick a user into loading a page containing malicious content, due to the way that the Edge Content Security Policy (CSP) validates certain specially crafted documents, aka "Microsoft Edge Security Feature Bypass Vulnerability". This CVE ID is unique from CVE-2017-8754.
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Analysis
by VulDB Data Team • 01/12/2021
The vulnerability described in CVE-2017-8723 represents a critical security flaw in Microsoft Edge browser's implementation of Content Security Policy (CSP) mechanisms within Windows 10 versions 1511, 1607, 1703, and Windows Server 2016. This security feature bypass vulnerability stems from improper validation of specially crafted documents that allows attackers to circumvent the intended security protections. The flaw specifically targets Edge's CSP implementation, which is designed to prevent cross-site scripting attacks and other code injection vulnerabilities by controlling which sources of content can be executed within web pages. When an attacker successfully exploits this vulnerability, they can trick users into loading malicious content that would normally be blocked by CSP restrictions, effectively neutralizing the browser's security controls.
The technical implementation flaw occurs in the way Microsoft Edge processes and validates CSP directives when encountering documents with specific formatting or content structures. This particular vulnerability operates as a security feature bypass rather than a direct code execution flaw, meaning that the attacker does not directly exploit a memory corruption or injection vulnerability but instead manipulates the browser's policy enforcement mechanisms. The vulnerability's impact is amplified by the fact that it affects multiple Windows 10 versions and Windows Server 2016, creating a widespread attack surface. According to CWE classification, this vulnerability would be categorized under CWE-284: Improper Access Control, as it allows unauthorized access to resources that should be restricted by security policies. The flaw essentially permits attackers to bypass the browser's intended security boundaries, potentially allowing for the execution of malicious scripts or the loading of unauthorized content that would normally be blocked by CSP enforcement.
The operational impact of this vulnerability extends beyond simple browser-based attacks and can enable more sophisticated exploitation techniques. Attackers can leverage this bypass to deliver malicious payloads through phishing campaigns, drive-by downloads, or compromised websites that appear legitimate to users. The security implications are particularly concerning because CSP is a fundamental security mechanism that protects against various attack vectors including cross-site scripting, data injection, and malicious code execution. When CSP validation is bypassed, it creates a chain reaction where other security controls may also be compromised. This vulnerability aligns with ATT&CK technique T1059.001: Command and Scripting Interpreter - PowerShell, as attackers can use the bypassed security controls to execute malicious PowerShell commands or other scripting languages within the victim's browser environment. The vulnerability essentially creates a persistent threat vector that can be used to establish footholds for more extensive attacks, making it particularly dangerous in enterprise environments where browser security is a critical defense layer.
Microsoft addressed this vulnerability through security updates that modified the CSP validation logic within Edge browser, ensuring that specially crafted documents no longer bypass the intended security controls. Organizations should implement comprehensive patch management procedures to ensure all affected Windows 10 systems and Windows Server 2016 installations receive the necessary updates. Additional mitigations include implementing network-level security controls such as web application firewalls, content filtering solutions, and enhanced browser hardening configurations. Security teams should also conduct regular vulnerability assessments to identify systems running affected versions of Windows 10 and ensure proper security posture maintenance. The vulnerability serves as a reminder of the importance of proper security policy enforcement and the need for continuous security validation of browser security mechanisms against evolving attack techniques.