CVE-2015-6766 in Chrome
Summary
by MITRE
Use-after-free vulnerability in the AppCache implementation in Google Chrome before 47.0.2526.73 allows remote attackers with renderer access to cause a denial of service or possibly have unspecified other impact by leveraging incorrect AppCacheUpdateJob behavior associated with duplicate cache selection.
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Analysis
by VulDB Data Team • 06/28/2022
The CVE-2015-6766 vulnerability represents a critical use-after-free flaw within Google Chrome's Application Cache (AppCache) implementation that existed in versions prior to 47.0.2526.73. This vulnerability falls under the CWE-416 category of Use After Free, which occurs when a program continues to reference memory after it has been freed, potentially leading to unpredictable behavior and exploitation. The issue specifically manifests in the AppCacheUpdateJob component, which is responsible for managing cache updates in Chrome's offline web application capabilities.
The technical exploitation of this vulnerability requires an attacker with renderer access to manipulate the AppCache system in a way that triggers incorrect behavior during duplicate cache selection processes. When Chrome's renderer processes attempt to handle multiple cache entries with identical identifiers, the AppCacheUpdateJob fails to properly manage memory allocation and deallocation sequences. This improper handling creates a scenario where freed memory objects are accessed again, leading to potential memory corruption that can result in application crashes or more severe consequences.
From an operational impact perspective, this vulnerability enables remote attackers to execute denial of service attacks against Chrome users by simply crafting malicious web content that triggers the flawed AppCache behavior. The potential for unspecified other impacts suggests that under certain conditions, this vulnerability could be leveraged for more sophisticated attacks beyond simple service disruption. The vulnerability's remote exploitability means that attackers do not require local system access or physical proximity to users, making it particularly dangerous in web-based attack scenarios.
The attack vector relies on the attacker's ability to control or influence content loaded in Chrome's renderer process, which can occur through various means including malicious websites, compromised web servers, or social engineering campaigns that trick users into visiting harmful content. This vulnerability demonstrates the inherent risks associated with complex web application caching mechanisms and highlights the importance of proper memory management in browser implementations. The flaw underscores the need for robust input validation and memory lifecycle management in web browser components that handle dynamic content processing.
Security practitioners should prioritize patching affected Chrome versions to address this vulnerability, as the use-after-free condition creates a potential pathway for privilege escalation or code execution attacks. The remediation process involves updating to Chrome version 47.0.2526.73 or later, which includes fixes to the AppCacheUpdateJob behavior and proper memory handling for duplicate cache selection scenarios. Organizations should also consider implementing additional security measures such as web application firewalls and content filtering systems to mitigate potential exploitation attempts while awaiting patch deployment. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage and T1489 for denial of service, demonstrating how browser vulnerabilities can enable broader attack frameworks.