CVE-2016-5258 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the WebRTC socket thread in Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 allows remote attackers to execute arbitrary code by leveraging incorrect free operations on DTLS objects during the shutdown of a WebRTC session.
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Analysis
by VulDB Data Team • 09/09/2022
The CVE-2016-5258 vulnerability represents a critical use-after-free flaw within Mozilla Firefox's WebRTC implementation that existed in versions prior to 48.0 and Firefox ESR 45.x before 45.3. This vulnerability specifically targets the WebRTC socket thread where improper memory management occurs during DTLS session shutdown procedures. The flaw arises from incorrect free operations on DTLS objects that are still referenced elsewhere in the application's memory space, creating a scenario where freed memory can be accessed and manipulated by malicious actors. Such vulnerabilities are particularly dangerous in browser environments where attackers can leverage web-based exploits to compromise user systems without requiring local privileges.
The technical implementation of this vulnerability stems from the WebRTC subsystem's handling of DTLS (Datagram Transport Layer Security) objects during session termination. When a WebRTC session concludes, the application attempts to free memory associated with DTLS objects, but fails to properly track all references to these objects. This memory management error creates a use-after-free condition where the freed memory block may be reallocated for other purposes while the application still maintains references to it. The flaw specifically manifests during the shutdown sequence of WebRTC sessions, making it particularly exploitable in scenarios where users interact with malicious web content that triggers WebRTC functionality.
The operational impact of CVE-2016-5258 extends beyond simple privilege escalation as it enables remote code execution capabilities that can be leveraged by attackers to gain complete control over affected systems. This vulnerability aligns with CWE-416 which describes the use of freed memory condition, and represents a classic example of how improper memory management in complex networking components can create severe security implications. Attackers can craft malicious web pages that, when loaded in affected Firefox versions, trigger the WebRTC shutdown process and subsequently exploit the use-after-free condition to execute arbitrary code with the privileges of the browser process. The vulnerability's remote exploitability means that users need only visit a compromised website to be at risk, making it particularly dangerous in the context of modern web browsing.
The exploitation of this vulnerability requires attackers to leverage specific conditions present in WebRTC session termination, making it more sophisticated than typical memory corruption flaws. The attack vector typically involves triggering a WebRTC session through JavaScript APIs, causing the session to terminate in a manner that exposes the memory management race condition. This vulnerability demonstrates the complexity of modern browser security where components like WebRTC, which handle real-time communication protocols, can introduce subtle memory management issues that are difficult to detect during normal development and testing processes. The flaw's classification under ATT&CK technique T1059.007 for command and scripting interpreter indicates that successful exploitation would enable attackers to execute malicious code through browser-based attack vectors.
Mitigation strategies for CVE-2016-5258 primarily focus on updating to patched versions of Firefox and Firefox ESR, as the vulnerability was resolved through proper memory management fixes in the WebRTC implementation. Organizations should implement immediate patch management protocols to ensure all affected browser installations are updated. Additional protective measures include implementing browser security policies that restrict WebRTC functionality, using content security policies to limit exposure to malicious WebRTC implementations, and monitoring for suspicious network activity that might indicate exploitation attempts. The vulnerability also highlights the importance of memory safety practices in browser development and underscores the need for comprehensive security testing of networking components that handle real-time communication protocols.