CVE-2020-6554 in Chrome
Summary
by MITRE
Use after free in extensions in Google Chrome prior to 84.0.4147.125 allowed a remote attacker to potentially perform a sandbox escape via a crafted Chrome Extension.
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Analysis
by VulDB Data Team • 05/05/2025
The vulnerability identified as CVE-2020-6554 represents a critical use-after-free flaw within Google Chrome's extension handling mechanisms that existed in versions prior to 84.0.4147.125. This issue stems from improper memory management during the processing of Chrome extensions, creating a scenario where freed memory locations could be accessed and potentially exploited by malicious actors. The vulnerability specifically affects the extension subsystem and demonstrates a fundamental failure in how Chrome manages memory allocation and deallocation for extension components. The flaw occurs when the browser processes certain crafted extension files, leading to a situation where extension objects are freed from memory but remain accessible to subsequent operations, creating potential exploitation vectors.
The technical nature of this vulnerability aligns with CWE-416, which describes the use of freed memory condition, and represents a sandbox escape vector that undermines Chrome's security model. When a malicious extension is loaded, the improper memory handling allows an attacker to manipulate freed memory locations through carefully crafted extension code. This enables the exploitation of a remote code execution vulnerability that could bypass Chrome's sandbox protections and potentially elevate privileges. The flaw operates by leveraging the extension API to trigger memory management issues, where extension objects are destroyed but their memory is not properly invalidated, allowing subsequent operations to access the freed memory space. This creates a pathway for attackers to inject malicious code that can execute outside of the intended sandbox boundaries.
The operational impact of CVE-2020-6554 extends beyond simple remote code execution, as it represents a significant compromise to Chrome's security architecture. Attackers could leverage this vulnerability to escape the sandbox environment that typically isolates extension processes from the underlying system, potentially gaining access to sensitive user data, system resources, and browser functionality. The vulnerability's remote nature means that exploitation could occur without user interaction, simply through the installation or loading of a malicious extension. This makes it particularly dangerous in environments where users may unknowingly install compromised extensions from the Chrome Web Store or other sources. The sandbox escape capability directly violates the fundamental security principle that extension processes should be isolated from the main browser and system processes, potentially allowing attackers to perform actions such as file system access, network communication, and privilege escalation.
Mitigation strategies for CVE-2020-6554 primarily focus on updating Chrome to version 84.0.4147.125 or later, which contains the necessary patches to address the memory management issues in extension handling. Organizations should implement proactive measures including monitoring for unauthorized extension installations and maintaining updated browser versions across all user environments. The vulnerability's classification under ATT&CK technique T1195.001 for "Supply Chain Compromise" highlights the importance of extension source verification and security monitoring. Security teams should also consider implementing browser hardening measures, such as disabling unnecessary extension APIs and monitoring for suspicious extension behavior. Additionally, user education regarding the risks of installing third-party extensions and the importance of only downloading extensions from trusted sources remains crucial. The patch for this vulnerability specifically addresses the memory management routines in Chrome's extension subsystem, ensuring proper invalidation of memory locations after object destruction and preventing the use-after-free conditions that enabled the sandbox escape. Organizations should also consider implementing extension whitelisting policies and regular security audits of installed extensions to prevent exploitation of similar vulnerabilities in the future.