CVE-2015-6757 in Chrome
Summary
by MITRE
Use-after-free vulnerability in content/browser/service_worker/embedded_worker_instance.cc in the ServiceWorker implementation in Google Chrome before 46.0.2490.71 allows remote attackers to cause a denial of service or possibly have unspecified other impact by leveraging object destruction in a callback.
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Analysis
by VulDB Data Team • 06/21/2022
The CVE-2015-6757 vulnerability represents a critical use-after-free flaw within Google Chrome's ServiceWorker implementation that existed in versions prior to 46.0.2490.71. This vulnerability specifically resides in the embedded_worker_instance.cc file within the content/browser/service_worker directory of Chrome's codebase. The ServiceWorker API provides a mechanism for web applications to intercept and handle network requests, manage background tasks, and enable features like push notifications and offline capabilities. When a ServiceWorker is registered and active, it operates in a separate process from the main web page, creating a complex interaction model between the browser's main thread and the service worker's embedded worker instance.
The technical flaw manifests when an object is destroyed during a callback execution context, creating a scenario where subsequent operations attempt to access memory that has already been freed. This particular vulnerability occurs in the service worker lifecycle management, specifically during the destruction phase of embedded worker instances. When a service worker is terminated or replaced, the embedded worker instance undergoes cleanup operations that involve callback functions. If these callbacks reference objects that have already been freed from memory, the application enters an undefined state where memory access violations can occur. This use-after-free condition can be exploited by remote attackers who craft malicious web content that triggers the specific sequence of operations leading to object destruction within the callback context.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more severe consequences including arbitrary code execution or information disclosure. When a remote attacker successfully exploits this vulnerability, they can cause the Chrome browser to crash or behave unpredictably, leading to service disruption for users. However, the potential for more serious exploitation exists due to the nature of use-after-free vulnerabilities, which can be leveraged to execute arbitrary code within the context of the browser process. The vulnerability affects the browser's ability to maintain stable operation during service worker lifecycle events, potentially allowing attackers to inject malicious code that executes with the privileges of the browser process. This creates a significant risk for users who browse the web with outdated Chrome versions, as the attack surface expands to include any web application that utilizes ServiceWorker functionality.
Mitigation strategies for CVE-2015-6757 primarily involve updating to Chrome version 46.0.2490.71 or later, which contains the necessary patches to address the object destruction timing issue in the ServiceWorker callback mechanism. Organizations should prioritize immediate deployment of this security update across all affected systems, particularly in enterprise environments where Chrome is widely used. Additionally, browser vendors and security teams should implement monitoring for exploitation attempts targeting this vulnerability, as use-after-free vulnerabilities often have a high potential for being weaponized. The vulnerability aligns with CWE-416, which describes the use of freed memory condition, and can be mapped to ATT&CK technique T1059.001 for the execution of malicious code through browser-based attacks. Security researchers should also consider implementing additional sandboxing measures and memory protection mechanisms to reduce the potential impact if such vulnerabilities are exploited in the wild. Regular security audits of browser components and service worker implementations should be conducted to identify similar timing-related memory management issues that could lead to similar exploitation vectors.