CVE-2018-18337 in Chrome
Summary
by MITRE
Incorrect handling of stylesheets leading to a use after free in Blink in Google Chrome prior to 71.0.3578.80 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/18/2023
The vulnerability identified as CVE-2018-18337 represents a critical use after free condition within the Blink rendering engine of Google Chrome, affecting versions prior to 71.0.3578.80. This flaw resides in the improper handling of stylesheets during the HTML page rendering process, creating a scenario where memory management becomes compromised. The issue manifests when Chrome processes crafted HTML content containing specific stylesheet configurations that trigger erroneous memory deallocation followed by subsequent memory access. Such improper memory management creates opportunities for attackers to manipulate heap memory structures and potentially execute arbitrary code. The vulnerability operates at the intersection of memory safety and web rendering, where the browser's stylesheet processing logic fails to properly track object lifecycles during dynamic content modification.
The technical exploitation of this vulnerability involves constructing a malicious HTML page that leverages specific CSS properties and rendering behaviors to trigger the use after free condition. When Chrome processes such malformed content, the Blink engine's stylesheet handling code deallocates memory associated with CSS objects while simultaneously maintaining references to those freed memory regions. This creates a scenario where subsequent memory operations can overwrite the freed memory with attacker-controlled data, leading to heap corruption. The flaw specifically relates to how the browser handles dynamic stylesheet modifications and object cleanup during page rendering cycles. Attackers can exploit this by crafting HTML documents that cause the browser to repeatedly create and destroy CSS objects while maintaining references to previously deallocated memory, ultimately allowing for memory corruption that can be leveraged for code execution.
The operational impact of CVE-2018-18337 extends beyond simple memory corruption, as it provides a potential pathway for remote code execution in the context of web browsing. This vulnerability affects all users of affected Chrome versions, making it particularly dangerous in environments where users may encounter malicious content through phishing attacks, compromised websites, or drive-by downloads. The exploitability of this flaw is enhanced by the fact that it requires no user interaction beyond visiting a malicious website, making it a prime target for automated exploitation campaigns. Security researchers have classified this vulnerability under CWE-416, which specifically addresses use after free conditions, and it aligns with ATT&CK technique T1059.001 for remote code execution through browser exploits. The vulnerability demonstrates how seemingly benign web content processing can become a vector for sophisticated attacks, particularly when memory management errors occur in widely used software components.
Mitigation strategies for CVE-2018-18337 primarily focus on immediate software updates to the latest Chrome versions where the vulnerability has been patched. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive updates promptly. Browser vendors have addressed this issue through memory safety improvements in the Blink engine's stylesheet handling code, including enhanced object lifecycle management and stricter memory deallocation protocols. Security teams should also consider implementing additional protective measures such as sandboxing, content security policies, and web application firewalls to reduce the potential impact of exploitation attempts. The vulnerability serves as a reminder of the critical importance of memory safety in browser implementations and highlights the need for continuous security auditing of core rendering components that handle dynamic content processing. Regular security assessments of web browsers and their underlying engines remain essential for identifying and addressing similar vulnerabilities before they can be exploited in the wild.