CVE-2015-6772 in Chrome
Summary
by MITRE
The DOM implementation in Blink, as used in Google Chrome before 47.0.2526.73, does not prevent javascript: URL navigation while a document is being detached, which allows remote attackers to bypass the Same Origin Policy via crafted JavaScript code that improperly interacts with a plugin.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-6772 represents a critical security flaw in the Blink rendering engine that powers Google Chrome and other web browsers. This issue stems from improper handling of document detachment events within the Document Object Model implementation, creating a window of opportunity for malicious actors to exploit browser security mechanisms. The vulnerability specifically affects Chrome versions prior to 47.0.2526.73, making it a significant concern for users running outdated browser versions. The flaw resides in how the browser processes javascript: URLs when documents are in the process of being removed from the DOM, allowing attackers to manipulate the navigation flow outside normal security boundaries.
The technical exploitation of this vulnerability involves leveraging the timing gap between document detachment and URL navigation processing. When a document is being removed from the browser's document tree, the Blink engine fails to properly validate javascript: URLs that attempt to navigate during this transitional state. This creates a scenario where malicious code can inject javascript: URLs that bypass the standard Same Origin Policy enforcement mechanisms. The vulnerability is particularly dangerous because it allows attackers to execute code that would normally be restricted by cross-origin security policies, enabling unauthorized access to resources that should be protected by origin-based security controls. This flaw operates at the intersection of DOM manipulation and URL handling, creating a path for privilege escalation through improper state management during document lifecycle events.
The operational impact of CVE-2015-6772 extends beyond simple cross-origin bypass capabilities, as it can enable sophisticated attacks including but not limited to data exfiltration, session hijacking, and privilege escalation within the browser context. Attackers can craft malicious JavaScript that exploits this timing vulnerability to access plugin interfaces that should be restricted, potentially leading to full system compromise if the plugin has elevated privileges. The vulnerability aligns with CWE-124, which addresses "Array Access with Incorrect Length Value," and demonstrates how improper state management during object lifecycle transitions can create security exploits. This issue also maps to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: JavaScript" and T1211 for "Exploitation for Defense Evasion" as it enables attackers to bypass security controls through legitimate scripting mechanisms.
Mitigation strategies for CVE-2015-6772 require immediate browser updates to versions 47.0.2526.73 and later, which contain the necessary patches to properly handle document detachment events and javascript: URL navigation. Organizations should implement comprehensive browser update policies to ensure all systems are running patched versions, as this vulnerability can be exploited through various attack vectors including malicious websites, phishing campaigns, and compromised web applications. Additional protective measures include implementing Content Security Policy headers that restrict javascript: URL execution, monitoring for suspicious navigation patterns, and maintaining awareness of the vulnerability's exploitation patterns. Security teams should also consider deploying web application firewalls that can detect and block malicious JavaScript patterns associated with this specific vulnerability, as the flaw represents a classic example of how improper state transitions in browser engines can create security bypass opportunities. The vulnerability serves as a reminder of the critical importance of proper lifecycle management in browser components and the potential consequences of timing-based security flaws in complex web rendering engines.