CVE-2020-6435 in Chrome
Summary
by MITRE
Insufficient policy enforcement in extensions in Google Chrome prior to 81.0.4044.92 allowed a remote attacker who had compromised the renderer process to bypass navigation restrictions via a crafted HTML page.
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Analysis
by VulDB Data Team • 05/09/2025
The vulnerability identified as CVE-2020-6435 represents a critical security flaw in Google Chrome's extension policy enforcement mechanisms that existed prior to version 81.0.4044.92. This issue stems from inadequate restrictions on how extensions can interact with navigation operations within the browser environment, creating a potential pathway for privilege escalation and unauthorized access to restricted resources. The flaw specifically affects the renderer process, which is a critical component responsible for executing web content and maintaining isolation between different browsing contexts. The vulnerability allows remote attackers to bypass established navigation restrictions that are typically enforced by Chrome's security model, potentially enabling malicious actors to navigate to restricted domains or access sensitive information that should be protected from extension interference.
The technical implementation of this vulnerability involves a flaw in Chrome's extension security model where the browser fails to properly validate or enforce navigation policies when extensions attempt to manipulate browser navigation operations. Extensions in Chrome operate under specific permissions and security boundaries, but this flaw allows compromised extensions to circumvent these boundaries through crafted HTML content. The renderer process, which handles the execution of web pages and extension code, becomes a vector for exploitation when it processes malicious HTML that manipulates navigation behavior in ways that should be restricted. This type of vulnerability falls under the CWE category of insufficient policy enforcement, specifically CWE-693, which deals with protection mechanisms that are not properly enforced or are bypassed through improper implementation.
The operational impact of CVE-2020-6435 extends beyond simple navigation bypass, as it represents a fundamental weakness in Chrome's security architecture that could enable more sophisticated attacks. When an attacker successfully compromises a renderer process, they can leverage this vulnerability to access restricted domains, potentially leading to data exfiltration, privilege escalation, or further exploitation of the system. The vulnerability is particularly concerning because it operates at a level that allows extensions to bypass security controls that are typically enforced by the browser's core security model. Attackers could craft HTML pages that, when loaded in a compromised browser environment, would enable extensions to perform unauthorized navigation operations that should be restricted. This creates a potential attack surface where malicious actors can bypass security controls that are essential for maintaining user privacy and system integrity.
The exploitation of this vulnerability aligns with several techniques documented in the ATT&CK framework, particularly those related to privilege escalation and defense evasion. The ability to bypass navigation restrictions through compromised extensions demonstrates how attackers can leverage existing browser capabilities to circumvent security controls. This vulnerability could be classified under ATT&CK technique T1059 for execution through web-based attacks and T1068 for privilege escalation through compromised processes. The flaw represents a critical gap in Chrome's security model where the renderer process fails to properly enforce the security boundaries that should exist between different browsing contexts and extension permissions. Organizations using older versions of Chrome are particularly vulnerable to this attack vector, as the vulnerability was addressed through updates that strengthened the enforcement of navigation policies within the browser's extension framework.
Mitigation strategies for CVE-2020-6435 primarily focus on immediate remediation through software updates and browser version management. Organizations should prioritize updating Chrome to version 81.0.4044.92 or later, where the vulnerability has been addressed through enhanced policy enforcement mechanisms. Additionally, administrators should implement strict browser security policies that limit extension permissions and monitor for unauthorized extension installations. The vulnerability highlights the importance of maintaining up-to-date browser software and implementing comprehensive security monitoring to detect potential exploitation attempts. Security teams should also consider deploying network-based detection mechanisms that can identify suspicious navigation patterns or attempts to access restricted resources. Regular security assessments of browser configurations and extension management practices can help identify potential vulnerabilities in the security model that could be exploited through similar mechanisms. The fix implemented by Google involved strengthening the enforcement of navigation restrictions within the renderer process, ensuring that extension code cannot bypass these security controls through crafted HTML content.