CVE-2016-2811 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the ServiceWorkerInfo class in the Service Worker subsystem in Mozilla Firefox before 46.0 allows remote attackers to execute arbitrary code via vectors related to the BeginReading method.
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Analysis
by VulDB Data Team • 07/27/2022
The vulnerability identified as CVE-2016-2811 represents a critical use-after-free condition within Mozilla Firefox's Service Worker subsystem, specifically affecting versions prior to 46.0. This flaw exists in the ServiceWorkerInfo class and manifests through improper memory management during the BeginReading method execution. Service Workers serve as background processes that enable features like push notifications, background sync, and offline capabilities in modern web browsers, making them integral components of the browser's architecture. The vulnerability arises when the browser fails to properly validate memory references after objects have been freed, creating opportunities for malicious code execution through crafted web content.
The technical implementation of this vulnerability involves the exploitation of memory corruption patterns that occur when ServiceWorkerInfo objects are manipulated during the BeginReading operation. When a Service Worker processes data, the system allocates memory for handling incoming information and subsequently frees this memory after processing completes. However, in the affected Firefox versions, the BeginReading method does not properly validate that referenced objects remain valid after memory deallocation, leading to a scenario where attackers can manipulate freed memory locations. This use-after-free condition creates a predictable memory layout that attackers can exploit to overwrite critical memory regions, ultimately allowing remote code execution with the privileges of the browser process.
From an operational perspective, this vulnerability presents significant risks to web application security as it enables remote attackers to execute arbitrary code on affected systems without requiring user interaction beyond visiting a malicious website. The attack vector leverages the Service Worker subsystem's functionality, which is commonly enabled in modern web applications, making the exploit surface widely accessible. Security researchers have classified this vulnerability under CWE-416, which specifically addresses use-after-free conditions, and it aligns with ATT&CK technique T1059.007 for execution through web applications. The impact extends beyond simple code execution to potentially allow full system compromise, as the browser process typically runs with the privileges of the logged-in user, providing attackers with access to sensitive data, file system operations, and network communications.
The remediation strategy for CVE-2016-2811 requires immediate upgrade to Firefox version 46.0 or later, where Mozilla implemented proper memory management controls within the ServiceWorkerInfo class. Additionally, system administrators should consider implementing network-level protections such as content security policies and web application firewalls to limit exposure to potentially malicious Service Worker implementations. The fix addresses the root cause by ensuring proper reference validation and memory deallocation procedures within the BeginReading method, preventing the exploitation of freed memory locations. Organizations should also conduct comprehensive security assessments of their web application environments to identify any custom Service Worker implementations that might be vulnerable to similar memory corruption patterns, as this vulnerability demonstrates the importance of rigorous memory management in browser security subsystems.