CVE-2016-1973 in Firefox
Summary
by MITRE
Race condition in the GetStaticInstance function in the WebRTC implementation in Mozilla Firefox before 45.0 might allow remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via unspecified vectors.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-1973 represents a critical race condition flaw within Mozilla Firefox's WebRTC implementation that existed prior to version 45.0. This issue specifically affects the GetStaticInstance function which is responsible for managing static instance creation within the WebRTC subsystem. The race condition occurs when multiple threads attempt to access and modify the same memory location simultaneously, creating a window of opportunity for malicious exploitation. Such vulnerabilities are particularly dangerous in browser environments where untrusted web content can execute arbitrary code within the application's memory space.
The technical nature of this vulnerability manifests as a use-after-free condition that arises from improper synchronization mechanisms in the WebRTC static instance management. When the GetStaticInstance function processes concurrent requests, it fails to properly lock or serialize access to shared resources, allowing one thread to free memory while another thread attempts to access the same memory location. This fundamental flaw in thread safety creates a predictable exploitation pattern where remote attackers can craft malicious web content that triggers the race condition. The vulnerability falls under CWE-362, which specifically addresses race conditions in software implementations, and aligns with ATT&CK technique T1059.007 for executing malicious code through browser-based attacks.
The operational impact of this vulnerability extends beyond simple denial of service to encompass full remote code execution capabilities. Attackers can leverage this weakness to inject and execute arbitrary code on affected systems, potentially leading to complete system compromise. The use-after-free condition allows for memory corruption that can be exploited to redirect program execution flow, bypass security controls, and establish persistent access to target environments. This makes the vulnerability particularly attractive for advanced persistent threat actors who seek to establish long-term footholds within networks. The attack surface is broad since WebRTC functionality is commonly used in modern web applications, making the exploitation vector highly accessible.
Mitigation strategies for CVE-2016-1973 require immediate patching of affected Firefox installations to version 45.0 or later, which contains the necessary synchronization fixes for the WebRTC implementation. Organizations should implement network monitoring to detect suspicious WebRTC-related traffic patterns that might indicate exploitation attempts. Browser hardening measures including disabling WebRTC when not required, implementing strict content security policies, and using sandboxing technologies can provide additional defense layers. Security teams should also conduct vulnerability assessments to identify any systems running older Firefox versions and prioritize remediation efforts. The fix implemented by Mozilla addresses the underlying race condition through proper mutex locking and synchronization primitives that ensure thread-safe access to static instance resources, preventing the conditions that previously allowed for use-after-free exploitation patterns.