CVE-2017-8637 in Edge
Summary
by MITRE
Microsoft Edge in Microsoft Windows 10 1703 allows an attacker to bypass Arbitrary Code Guard (ACG) due to how Microsoft Edge accesses memory in code compiled by the Edge Just-In-Time (JIT) compiler, aka "Scripting Engine Security Feature Bypass Vulnerability".
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Analysis
by VulDB Data Team • 01/07/2021
The vulnerability identified as CVE-2017-8637 represents a critical security flaw in Microsoft Edge browser's implementation of Arbitrary Code Guard (ACG) protection mechanism within Windows 10 version 1703. This issue specifically targets the scripting engine's handling of memory access patterns during Just-In-Time compilation processes, creating a pathway for attackers to circumvent fundamental security protections designed to prevent code execution in restricted memory regions. The flaw manifests when Edge's JavaScript engine processes code compiled by its JIT compiler, allowing malicious actors to execute arbitrary code that would normally be blocked by ACG safeguards.
The technical root cause of this vulnerability lies in how Microsoft Edge's scripting engine manages memory access controls when processing JIT-compiled code. During the compilation process, the Edge JavaScript engine generates machine code that should be subject to ACG protections, which are designed to prevent execution of code in memory regions that are not intended for code execution. However, the vulnerability allows attackers to manipulate memory access patterns such that code can be executed in locations where ACG would normally prevent such operations. This bypass occurs specifically within the edge.js engine's memory management routines when handling compiled JavaScript code, creating a direct pathway for privilege escalation and code injection attacks.
The operational impact of CVE-2017-8637 is significant as it enables attackers to perform sophisticated exploitation techniques that would otherwise be prevented by modern security mitigations. Attackers can leverage this vulnerability to execute malicious code with elevated privileges, potentially leading to full system compromise. The vulnerability is particularly dangerous in targeted attacks where adversaries seek to establish persistent access or escalate privileges within compromised systems. The bypass of ACG protections means that traditional exploit mitigation techniques become ineffective, allowing attackers to execute shellcode or other malicious payloads that would normally be blocked by memory protection mechanisms.
This vulnerability aligns with CWE-119 Improper Access to Memory and CWE-787 Out-of-bounds Write patterns, as it involves improper memory access control during code execution and allows for memory corruption that bypasses protection mechanisms. From an ATT&CK framework perspective, this vulnerability maps to T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, as it enables attackers to execute malicious scripts and subsequently escalate privileges. The vulnerability also relates to T1190 Exploit Public-Facing Application, as it represents an exploitable weakness in a widely deployed browser application that can be leveraged from external attack vectors.
Mitigation strategies for CVE-2017-8637 primarily involve applying Microsoft's security patches and updates as released through Windows Update mechanisms. Organizations should prioritize immediate deployment of the relevant security updates to prevent exploitation. Additionally, implementing browser hardening measures such as disabling unnecessary JavaScript features, employing enhanced browser isolation techniques, and deploying application whitelisting policies can provide additional defense layers. Network-based protections including web application firewalls and intrusion detection systems should be configured to monitor for exploitation attempts targeting this specific vulnerability. Regular security assessments and vulnerability scanning should be conducted to identify systems that may be running unpatched versions of Microsoft Edge, as the vulnerability affects the specific Windows 10 1703 release and subsequent versions that have not received the appropriate security fixes.