CVE-2020-6391 in Chrome
Summary
by MITRE
Insufficient validation of untrusted input in Blink in Google Chrome prior to 80.0.3987.87 allowed a local attacker to bypass content security policy via a crafted HTML page.
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Analysis
by VulDB Data Team • 03/30/2024
The vulnerability identified as CVE-2020-6391 represents a critical security flaw in the Blink rendering engine that powers Google Chrome and other Chromium-based browsers. This issue stems from insufficient validation of untrusted input within the browser's core rendering component, creating a pathway for malicious actors to exploit the system's content security policy mechanisms. The vulnerability specifically affects Chrome versions prior to 80.0.3987.87, where the browser's security controls fail to properly validate HTML content that could potentially bypass established security boundaries. The flaw allows a local attacker to craft malicious HTML pages that can circumvent the browser's built-in protections, effectively undermining the security model designed to prevent unauthorized access to system resources.
The technical implementation of this vulnerability resides in the way Blink processes untrusted HTML input, particularly when handling elements that should be restricted by content security policy directives. When a user encounters a crafted HTML page, the browser's rendering engine fails to properly validate the input before executing potentially dangerous operations. This validation gap creates an opportunity for attackers to inject code or manipulate browser behavior in ways that should have been prevented by the content security policy framework. The flaw demonstrates a classic case of insufficient input sanitization where the system assumes certain HTML elements are safe without proper verification of their content or execution context. This weakness aligns with CWE-20, which describes insufficient input validation, and represents a failure in the browser's defense-in-depth approach to handling untrusted data.
The operational impact of CVE-2020-6391 extends beyond simple privilege escalation, as it enables attackers to bypass fundamental security mechanisms that protect users from malicious content. A local attacker could craft HTML pages that appear benign but contain hidden malicious elements designed to exploit this validation gap. The consequences could include unauthorized access to sensitive data, execution of arbitrary code, or manipulation of browser behavior in ways that compromise user privacy and system integrity. This vulnerability particularly affects users who may inadvertently visit malicious websites or receive crafted HTML content through social engineering attacks, as the exploitation requires only local access to the target system. The security implications are significant because content security policy is a crucial defense mechanism in modern web browsers, and its bypass undermines the trust model that users place in their browser's security features.
Mitigation strategies for this vulnerability require immediate patching of affected Chrome versions to ensure the browser's content security policy enforcement mechanisms function correctly. Organizations should implement comprehensive browser update policies to maintain current versions that contain the necessary security fixes. Additional protective measures include deploying web application firewalls that can detect and block suspicious HTML content, implementing strict content security policy headers on web applications, and educating users about the risks of visiting untrusted websites. From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1059 which covers command and scripting interpreter usage, and T1211 which addresses exploitation for defense evasion. Security teams should also consider implementing monitoring solutions that can detect anomalous browser behavior patterns that might indicate exploitation attempts, particularly focusing on content security policy violations and unexpected HTML rendering behaviors.