CVE-2020-6439 in Chrome
Summary
by MITRE
Insufficient policy enforcement in navigations in Google Chrome prior to 81.0.4044.92 allowed a remote attacker to bypass security UI via a crafted HTML page.
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Analysis
by VulDB Data Team • 05/09/2025
The vulnerability identified as CVE-2020-6439 represents a critical flaw in Google Chrome's security model that existed prior to version 81.0.4044.92. This issue stems from insufficient policy enforcement during navigation operations, creating a pathway for remote attackers to circumvent established security user interfaces. The flaw specifically targets Chrome's handling of navigation requests and the associated security warnings that should normally prevent potentially dangerous operations from proceeding without proper user consent.
This vulnerability operates at the intersection of browser security architecture and user interface protection mechanisms. When Chrome processes navigation requests, it typically enforces security policies that display warnings to users before allowing transitions to potentially unsafe destinations. However, the flaw in CVE-2020-6439 allowed malicious actors to craft HTML pages that could bypass these critical security checks, effectively disabling the protective mechanisms that users rely on for safe browsing. The technical implementation involves manipulating navigation flows in ways that exploit gaps in Chrome's policy enforcement logic, particularly around how the browser handles cross-origin navigation and security boundary checks.
The operational impact of this vulnerability is significant as it undermines fundamental browser security assumptions that users depend upon for protection against phishing attacks, malicious redirects, and other navigation-based threats. Attackers could potentially exploit this flaw to redirect users to malicious sites without triggering the expected security warnings, making it easier to conduct social engineering attacks and phishing campaigns. The vulnerability particularly affects users who rely on Chrome's security UI for protection against suspicious navigation attempts, as the bypass mechanism operates silently without alerting users to the compromised security state. This creates a dangerous scenario where users may unknowingly navigate to harmful destinations while believing they are protected by standard security measures.
From a cybersecurity perspective, this vulnerability aligns with CWE-693, which addresses Protection Mechanism Failure, and demonstrates how navigation-based security mechanisms can be circumvented through insufficient policy enforcement. The ATT&CK framework categorizes this type of vulnerability under T1059 for Command and Scripting Interpreter and potentially T1566 for Phishing, as it enables more effective social engineering attacks by removing protective barriers. Organizations should implement immediate mitigation strategies including mandatory Chrome updates to version 81.0.4044.92 or later, alongside enhanced monitoring for suspicious navigation patterns and user behavior anomalies. Security teams should also consider implementing additional network-level protections and user education programs to address the potential for exploitation, particularly in environments where users may be targeted by sophisticated phishing campaigns that leverage such browser vulnerabilities.