CVE-2020-12416 in Firefox
Summary
by MITRE
A VideoStreamEncoder may have been freed in a race condition with VideoBroadcaster::AddOrUpdateSink, resulting in a use-after-free, memory corruption, and a potentially exploitable crash. This vulnerability affects Firefox < 78.
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Analysis
by VulDB Data Team • 07/10/2020
This vulnerability represents a critical use-after-free condition that emerged in the Firefox browser's media streaming components, specifically within the VideoStreamEncoder and VideoBroadcaster subsystems. The flaw occurs when a VideoStreamEncoder object is prematurely deallocated while another thread is simultaneously attempting to access it through the VideoBroadcaster::AddOrUpdateSink method. This race condition creates a scenario where memory previously freed by one thread becomes accessible to another thread, leading to unpredictable behavior and potential exploitation.
The technical nature of this vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software systems. The race condition manifests when multiple threads operate concurrently on shared memory resources without proper synchronization mechanisms. In this case, the VideoBroadcaster::AddOrUpdateSink method does not adequately protect against concurrent access to the VideoStreamEncoder object, allowing for a timing window where the object can be destroyed while still being referenced. This creates a memory corruption scenario that can be leveraged by malicious actors to execute arbitrary code.
The operational impact of CVE-2020-12416 extends beyond simple browser instability, as it provides a potential pathway for remote code execution. When exploited, the vulnerability can cause the browser to crash or behave unpredictably, potentially allowing attackers to inject malicious code into the victim's system. The vulnerability affects Firefox versions prior to 78, meaning users running older versions face significant risk. The exploitability of this condition is enhanced by the fact that media streaming operations are common in web browsing, making the attack surface relatively accessible to threat actors.
Mitigation strategies for this vulnerability require immediate patching of affected Firefox installations to version 78 or later, where the race condition has been addressed through proper synchronization mechanisms. Organizations should implement comprehensive browser update policies and ensure all users are running patched versions. The fix typically involves introducing proper locking mechanisms or atomic operations within the VideoBroadcaster::AddOrUpdateSink method to prevent concurrent access to the VideoStreamEncoder object. Additionally, security teams should monitor for any attempts to exploit this vulnerability through network traffic analysis and implement intrusion detection systems that can identify potential exploitation attempts. This vulnerability also highlights the importance of thorough testing for race conditions in multimedia and streaming components, as these areas often contain complex threading scenarios that can introduce security flaws. The ATT&CK framework categorizes this vulnerability under T1203, which covers exploitation for execution through the use of memory corruption vulnerabilities, emphasizing the need for proper memory management practices in web browser implementations.