CVE-2017-8521 in Edge
Summary
by MITRE
Microsoft Edge in Windows 10 1703 allows an attacker to execute arbitrary code in the context of the current user when the Edge JavaScript scripting engine fails to handle objects in memory, aka "Scripting Engine Memory Corruption Vulnerability". This CVE ID is unique from CVE-2017-8499, CVE-2017-8520, CVE-2017-8548, and CVE-2017-8549.
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Analysis
by VulDB Data Team • 12/28/2020
The vulnerability described in CVE-2017-8521 represents a critical memory corruption flaw within Microsoft Edge's JavaScript scripting engine that affects Windows 10 version 1703. This issue arises from improper handling of objects in memory during JavaScript execution, creating a pathway for remote code execution attacks. The vulnerability specifically targets the v8 JavaScript engine component that powers Microsoft Edge's web rendering capabilities, making it particularly dangerous given Edge's widespread use as the default browser on Windows 10 systems. Security researchers have classified this as a scripting engine memory corruption vulnerability, which falls under the broader category of memory safety issues that have historically been exploited in browser-based attacks.
The technical exploitation of this vulnerability occurs when Edge's JavaScript engine fails to properly manage memory objects during script execution, leading to memory corruption that can be leveraged by malicious actors to execute arbitrary code with the privileges of the currently logged-in user. This memory corruption typically manifests through buffer overflows, use-after-free conditions, or other memory management errors that allow attackers to overwrite critical memory locations. The flaw specifically impacts the JavaScript engine's object handling mechanisms, where improper memory allocation and deallocation processes create exploitable conditions that can be triggered through malicious web content. Attackers can craft specially designed web pages that, when loaded in Edge, trigger the memory corruption and subsequently execute malicious payloads.
The operational impact of CVE-2017-8521 is severe given that it allows for privilege escalation attacks without requiring administrative privileges or user interaction beyond visiting a malicious webpage. This vulnerability enables attackers to gain persistent access to affected systems, potentially leading to full system compromise through subsequent exploitation or lateral movement within network environments. The attack surface is particularly broad since Edge is the default browser on Windows 10 systems, making it accessible to attackers through various vectors including phishing emails, compromised websites, or drive-by downloads. Once exploited, the vulnerability can be used to establish backdoors, steal sensitive data, install additional malware, or serve as a foothold for more extensive attacks within corporate networks. The vulnerability's classification aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write conditions, both of which are common memory corruption patterns.
Mitigation strategies for CVE-2017-8521 should prioritize immediate patching of affected Windows 10 systems with the Microsoft security update released in August 2017. Organizations should implement network-based protections such as web application firewalls and content filtering systems to block access to known malicious domains. Browser hardening measures including disabling unnecessary JavaScript features, implementing strict content security policies, and using sandboxing technologies can reduce the attack surface. Security teams should monitor for indicators of compromise related to this vulnerability, including unusual network connections, unauthorized file modifications, or unexpected process executions. The vulnerability also highlights the importance of keeping all browser components updated and implementing defense-in-depth strategies that include regular security assessments, user education about phishing risks, and maintaining up-to-date antivirus signatures that can detect exploitation attempts. This vulnerability demonstrates the critical nature of browser security and the potential for scripting engine flaws to serve as primary attack vectors in modern cyber warfare campaigns, aligning with tactics documented in the MITRE ATT&CK framework under the technique of "Exploitation for Privilege Escalation" and "Execution through Web-based Applications".