CVE-2016-5254 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the nsXULPopupManager::KeyDown function in Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 allows attackers to execute arbitrary code or cause a denial of service (heap memory corruption and application crash) by leveraging keyboard access to use the Alt key during selection of top-level menu items.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability identified as CVE-2016-5254 represents a critical use-after-free flaw within Mozilla Firefox's XUL popup management system. This issue affects Firefox versions prior to 48.0 and Firefox ESR 45.x versions before 45.3, where the nsXULPopupManager::KeyDown function fails to properly manage memory allocation and deallocation during keyboard interaction with menu items. The flaw specifically manifests when users employ the Alt key to navigate through top-level menu selections, creating a scenario where freed memory locations are accessed after being reclaimed by the system's heap management.
The technical nature of this vulnerability stems from improper memory management practices within the browser's user interface rendering engine. When a user presses the Alt key while navigating menu items, the nsXULPopupManager component processes keyboard input events and manages popup window states. The use-after-free condition occurs because the function does not adequately validate that referenced memory objects remain valid after certain operations, particularly when handling menu item selection and popup display transitions. This memory corruption vulnerability falls under CWE-416, which specifically addresses use-after-free conditions where memory is accessed after it has been freed, creating potential exploitation vectors for malicious actors.
The operational impact of this vulnerability extends beyond simple application instability, presenting significant security risks to users. Attackers can leverage this flaw to execute arbitrary code on vulnerable systems, effectively bypassing standard security boundaries and potentially gaining full control over the affected browser environment. The heap memory corruption that occurs during exploitation can lead to unpredictable application behavior, including crashes, data corruption, or more dangerous scenarios where malicious code injection becomes possible. This vulnerability directly impacts the browser's security model and can be exploited in various attack scenarios, including drive-by downloads, malicious website exploitation, and targeted attacks against unsuspecting users.
The exploitation of CVE-2016-5254 aligns with several tactics outlined in the MITRE ATT&CK framework, particularly those related to privilege escalation and code execution through browser-based attacks. The vulnerability can be classified under the Tactic of Execution and the Technique of Command and Scripting Interpreter, as attackers can leverage the heap corruption to run malicious code within the browser context. Security professionals should note that this issue demonstrates the critical importance of proper memory management in browser components, as even seemingly benign user interactions like keyboard navigation can become attack vectors when memory handling is inadequate.
Organizations and users should prioritize immediate patching of affected Firefox installations to mitigate this vulnerability, as the use-after-free condition can be reliably exploited without requiring special privileges or complex attack scenarios. The remediation process involves updating to Firefox 48.0 or Firefox ESR 45.3, which contain the necessary memory management fixes to prevent the improper handling of freed memory objects. Additionally, security teams should implement monitoring for potential exploitation attempts and consider deploying additional browser hardening measures, including content security policies and sandboxing configurations, to reduce the overall attack surface and limit potential damage from successful exploitation attempts.