CVE-2015-1243 in Chrome
Summary
by MITRE
Use-after-free vulnerability in the MutationObserver::disconnect function in core/dom/MutationObserver.cpp in the DOM implementation in Blink, as used in Google Chrome before 42.0.2311.135, allows remote attackers to cause a denial of service or possibly have unspecified other impact by triggering an attempt to unregister a MutationObserver object that is not currently registered.
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Analysis
by VulDB Data Team • 05/10/2022
The CVE-2015-1243 vulnerability represents a critical use-after-free flaw within the Blink rendering engine's DOM implementation that affected Google Chrome versions prior to 42.0.2311.135. This vulnerability resides in the MutationObserver::disconnect function located in core/dom/MutationObserver.cpp, which is a core component of the web browser's document object model handling capabilities. The flaw manifests when the MutationObserver object attempts to unregister itself from the DOM event system, creating a scenario where memory management becomes compromised. The vulnerability operates under CWE-416, which specifically addresses use-after-free conditions where a pointer is used after the memory it references has been freed, making it a classic example of memory safety issues in web browser implementations.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious web content that triggers the MutationObserver::disconnect function with an improperly managed object reference. When a MutationObserver attempts to disconnect from the DOM, but the object is already in an unregistered state or has been freed from memory, the system attempts to access freed memory locations. This creates a scenario where the browser's memory management system becomes corrupted, potentially leading to arbitrary code execution or complete application crash. The vulnerability is particularly dangerous because it can be triggered remotely through web pages, making it a prime target for drive-by download attacks and cross-site scripting exploits. The impact extends beyond simple denial of service as the use-after-free condition could potentially be leveraged for privilege escalation or information disclosure attacks, depending on the specific memory layout and execution context.
The operational impact of CVE-2015-1243 is severe for organizations relying on affected Chrome versions, as it provides attackers with a reliable method for causing system instability and potentially executing malicious code. The vulnerability affects the core DOM manipulation capabilities of the browser, which means that any web page could potentially exploit this flaw, making it extremely difficult to defend against through traditional network security measures. Attackers can leverage this vulnerability in conjunction with other exploitation techniques to create more sophisticated attacks, particularly when combined with sandbox escape mechanisms or other browser vulnerabilities. The vulnerability's presence in the Blink engine means that all browsers using this rendering engine were affected, including Chrome, Chromium, and derivative products. This widespread impact makes the vulnerability particularly concerning for enterprise environments where multiple systems may be running vulnerable versions of Chrome.
Mitigation strategies for CVE-2015-1243 primarily focus on immediate patching and version updates to Chrome 42.0.2311.135 or later, which contains the necessary memory management fixes for the MutationObserver::disconnect function. Organizations should implement comprehensive patch management processes to ensure all affected systems receive updates promptly, as the vulnerability can be exploited without user interaction through malicious web content. Browser hardening measures including sandboxing, content security policies, and restricted JavaScript execution can provide additional layers of protection, though these do not fully address the underlying memory safety issue. Network-based mitigations such as web application firewalls and content filtering can help reduce exposure by blocking suspicious web content, but the most effective solution remains immediate software patching. The vulnerability also highlights the importance of regular security assessments and code reviews focusing on memory management patterns, particularly in core browser components that handle DOM manipulation and event handling. Security teams should monitor for related vulnerabilities in the Blink engine and implement proactive threat hunting to identify potential exploitation attempts that might leverage similar memory safety flaws.