CVE-2015-6767 in Chrome
Summary
by MITRE
Use-after-free vulnerability in content/browser/appcache/appcache_dispatcher_host.cc in the AppCache implementation in Google Chrome before 47.0.2526.73 allows remote attackers to cause a denial of service or possibly have unspecified other impact by leveraging incorrect pointer maintenance associated with certain callbacks.
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Analysis
by VulDB Data Team • 06/28/2022
The CVE-2015-6767 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 resides in the appcache_dispatcher_host.cc file, which governs the communication between the browser's main process and the application cache subsystem. The flaw stems from improper pointer management during callback execution, creating a scenario where memory locations could be accessed after they have been freed, potentially leading to unpredictable behavior and system instability.
The technical exploitation of this vulnerability occurs when the AppCache subsystem handles certain callbacks that involve memory operations. During normal operation, the application cache maintains references to various objects and resources that are managed through pointer-based memory management. However, the implementation fails to properly maintain these pointers during asynchronous callback execution, allowing a remote attacker to manipulate the timing and sequence of operations to trigger a use-after-free condition. This mismanagement creates a race condition where freed memory addresses are accessed by subsequent operations, potentially leading to memory corruption that could be exploited for arbitrary code execution or denial of service.
From an operational impact perspective, this vulnerability poses significant risks to Chrome users as it can be leveraged remotely through web content. The attack surface is broad since the AppCache functionality is commonly used by websites for offline capabilities and progressive web applications. When exploited, the vulnerability can cause Chrome to crash and restart, leading to denial of service for the affected user. More concerning is the potential for unspecified other impacts that could include privilege escalation or remote code execution, depending on the specific memory corruption patterns and the attacker's ability to control the execution flow. The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software implementations.
The exploitation of this vulnerability requires an attacker to craft malicious web content that triggers the specific code path involving the AppCache callbacks. This typically involves creating web pages that utilize application cache APIs in ways that cause the browser to execute the problematic code sequence. The attack can be delivered through various vectors including compromised websites, malicious advertisements, or phishing pages. Security researchers have identified that the vulnerability is particularly dangerous because it can be triggered without user interaction beyond visiting a malicious webpage, making it a prime target for automated exploitation campaigns. Organizations should consider this vulnerability in their threat modeling and incident response planning, as it represents a persistent risk for users running vulnerable versions of Chrome.
Mitigation strategies for CVE-2015-6767 primarily involve updating to Chrome version 47.0.2526.73 or later, which contains the necessary patches to address the pointer management issues. Browser vendors and system administrators should prioritize immediate deployment of these updates across all affected systems. Additional protective measures include implementing content security policies that limit the use of application cache APIs where possible, and monitoring for unusual browser behavior or crashes that might indicate exploitation attempts. Organizations should also consider deploying web application firewalls or security proxies that can detect and block malicious content targeting this vulnerability. The remediation process should include thorough testing of updates in controlled environments before widespread deployment to ensure compatibility with existing applications and services. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of vulnerable software within the organization's infrastructure.