CVE-2017-5121 in Chrome
Summary
by MITRE
Inappropriate use of JIT optimisation in V8 in Google Chrome prior to 61.0.3163.100 for Linux, Windows, and Mac allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted HTML page, related to the escape analysis phase.
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Analysis
by VulDB Data Team • 01/05/2023
The vulnerability CVE-2017-5121 represents a critical security flaw in Google Chrome's V8 JavaScript engine that existed prior to version 61.0.3163.100 across multiple platforms including Linux, Windows, and Mac operating systems. This issue stems from an improper implementation of Just-In-Time compilation optimizations specifically during the escape analysis phase of code execution. The escape analysis is a compiler optimization technique that determines whether local variables can be allocated on the stack or must be heap-allocated, and when this process is incorrectly handled, it creates exploitable conditions within the browser's sandbox environment. The flaw manifests when Chrome processes maliciously crafted HTML content that triggers the problematic JIT optimization path, allowing attackers to bypass the security boundaries that normally isolate web content from the underlying operating system.
The technical exploitation of this vulnerability occurs through a sophisticated attack vector that leverages the V8 engine's optimization process to achieve remote code execution within the browser's sandboxed environment. During the escape analysis phase, the compiler incorrectly handles certain variable scope analyses, creating memory corruption conditions that can be manipulated by attackers. This misconfiguration allows a remote adversary to craft HTML pages containing malicious JavaScript code that when executed triggers the faulty JIT optimization path. The vulnerability specifically targets the interaction between the V8 compiler's optimization passes and memory management routines, where improper handling of escape analysis results leads to memory layout corruption that can be exploited to gain arbitrary code execution privileges. The attack requires the victim to visit a malicious webpage containing the crafted HTML content, making it a typical web-based exploit that can be delivered through various attack vectors including phishing campaigns, compromised websites, or malicious advertisements.
The operational impact of CVE-2017-5121 is severe as it fundamentally undermines the security model that Chrome employs to isolate web content from the host system. The vulnerability allows attackers to execute arbitrary code within the browser's sandbox, effectively breaking the security boundary that separates trusted browser components from potentially malicious web content. This represents a privilege escalation scenario where remote attackers can gain elevated execution privileges without requiring user interaction beyond visiting a malicious webpage. The exploitation can lead to complete system compromise, data theft, or further attack propagation within the victim's network environment. Organizations running affected Chrome versions face significant risk as this vulnerability can be exploited in the wild without user awareness, making it particularly dangerous for enterprise environments where users frequently browse the internet and encounter untrusted content.
This vulnerability aligns with CWE-122, which describes improper restriction of operations within a memory buffer, and maps to ATT&CK technique T1059.007 for JavaScript-based execution. The flaw demonstrates how compiler optimization techniques can introduce security vulnerabilities when not properly validated against security requirements. The escape analysis phase in V8's JIT compiler is particularly susceptible to this type of attack because it involves complex memory management decisions that can be manipulated through carefully crafted input. Security researchers have identified that the vulnerability occurs due to insufficient bounds checking during the optimization process, where the compiler fails to properly validate memory access patterns during variable escape analysis. Organizations should implement immediate mitigations including updating to Chrome version 61.0.3163.100 or later, deploying web application firewalls, and monitoring for suspicious web traffic patterns that might indicate exploitation attempts. Additionally, browser hardening measures such as disabling unnecessary JavaScript features, implementing strict content security policies, and maintaining up-to-date security patches across all systems can help reduce the attack surface and mitigate the risk associated with this vulnerability.