CVE-2018-6164 in Chrome
Summary
by MITRE
Insufficient origin checks for CSS content in Blink in Google Chrome prior to 68.0.3440.75 allowed a remote attacker to leak cross-origin data via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/26/2023
The vulnerability identified as CVE-2018-6164 represents a critical security flaw in the Blink rendering engine that powers Google Chrome and other Chromium-based browsers. This issue stems from inadequate origin validation mechanisms within the CSS content processing pipeline, creating a pathway for malicious actors to bypass fundamental web security boundaries. The vulnerability specifically affects Chrome versions prior to 68.0.3440.75, where the browser's security model failed to properly enforce same-origin policies when handling CSS content, potentially allowing unauthorized data access across different origins.
The technical implementation of this vulnerability exploits the way Blink processes CSS content from external sources, particularly when cross-origin resources are involved. When a malicious webpage loads CSS content from a different origin, the browser's origin checking mechanisms should prevent access to sensitive data or resources that belong to other domains. However, in affected versions, these checks were insufficiently robust, allowing attackers to craft HTML pages that could trigger specific CSS behaviors to extract information from cross-origin resources. This flaw operates at the intersection of browser security architecture and CSS processing, where the rendering engine's failure to properly validate resource origins creates a vector for data leakage.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables sophisticated cross-origin attacks that could potentially lead to more severe consequences. Attackers could leverage this weakness to gather sensitive information from other domains, including user data, session tokens, or private content that should remain isolated between different origins. The remote nature of this attack means that exploitation requires no local system access or user interaction beyond visiting a malicious webpage, making it particularly dangerous in phishing campaigns or compromised websites. This vulnerability directly violates core web security principles established by the same-origin policy, which is fundamental to preventing unauthorized cross-site data access.
Security professionals should note that this vulnerability aligns with CWE-200 (Information Exposure) and relates to ATT&CK technique T1071.001 (Application Layer Protocol: Web Protocols) in its exploitation methods. The remediation strategy involves updating to Chrome version 68.0.3440.75 or later, where Google implemented enhanced origin validation for CSS content processing. Organizations should also consider implementing additional network-level protections such as content security policies and strict origin checks in their web applications. Browser vendors and security teams should prioritize monitoring for similar vulnerabilities in CSS processing and other rendering engine components that could potentially bypass cross-origin security boundaries. The fix demonstrates the importance of rigorous security testing for browser rendering engines and highlights the critical need for comprehensive origin validation mechanisms in web browsers.