CVE-2016-9068 in Firefox
Summary
by MITRE
A use-after-free during web animations when working with timelines resulting in a potentially exploitable crash. This vulnerability affects Firefox < 50.
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Analysis
by VulDB Data Team • 01/31/2018
The vulnerability identified as CVE-2016-9068 represents a critical use-after-free condition that occurs within the Firefox browser's web animation processing subsystem. This flaw specifically manifests when the browser handles timeline-based animations, creating a scenario where memory that has been freed is subsequently accessed by the application. The vulnerability affects Firefox versions prior to 50, indicating it was present in a significant portion of the browser's user base during the affected timeframe. The root cause stems from improper memory management within the browser's rendering engine, particularly in how it processes animation timelines and manages the lifecycle of animation objects.
The technical exploitation of this vulnerability occurs through a carefully crafted web page that triggers the specific code path leading to the use-after-free condition. When Firefox processes timeline-based animations, the browser's animation engine creates and manages various objects in memory including timeline references and animation frame data. The flaw emerges when the timeline management code fails to properly track object lifecycles, allowing an animation object to be freed from memory while references to it remain active within the timeline processing logic. This creates a scenario where subsequent operations attempt to access memory that has already been deallocated, resulting in a crash that can potentially be leveraged for remote code execution.
The operational impact of CVE-2016-9068 extends beyond simple browser instability, as it represents a potential remote code execution vector that could be exploited by malicious actors. The vulnerability's classification aligns with CWE-416, which describes the use of freed memory condition, and demonstrates how improper memory management can lead to severe security implications. Attackers could craft malicious web pages that, when loaded in vulnerable Firefox versions, would trigger the use-after-free condition and potentially allow arbitrary code execution with the privileges of the browser process. This makes the vulnerability particularly dangerous in environments where users browse untrusted web content, as the attack surface is broad and the exploitation mechanism is relatively straightforward to implement.
The exploitation of this vulnerability follows patterns consistent with the attack techniques described in the MITRE ATT&CK framework under the T1059 category for command and scripting interpreter, as attackers would leverage the browser's JavaScript engine to execute malicious code through the vulnerable animation processing path. Security researchers have noted that the crash behavior is predictable enough to be weaponized, with the use-after-free allowing for memory corruption that can be leveraged to control program execution flow. Organizations using affected Firefox versions should prioritize immediate patching, as the vulnerability was actively exploited in the wild during its disclosure period. The fix implemented by Mozilla in Firefox 50 involved proper memory management within the animation timeline processing code, ensuring that animation objects are properly tracked and freed only when no longer referenced, thereby preventing the use-after-free condition from occurring.