CVE-2016-2839 in Firefox
Summary
by MITRE
Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 on Linux make cairo _cairo_surface_get_extents calls that do not properly interact with libav header allocation in FFmpeg 0.10, which allows remote attackers to cause a denial of service (application crash) via a crafted video.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability identified as CVE-2016-2839 represents a critical denial of service weakness affecting Mozilla Firefox versions prior to 48.0 and Firefox ESR 45.x versions before 45.3 on Linux systems. This flaw specifically manifests when Firefox attempts to process video content through its media handling capabilities, creating a scenario where the application becomes susceptible to crashes due to improper interaction between its graphics rendering subsystem and underlying multimedia libraries. The issue stems from how Firefox's cairo graphics library interfaces with FFmpeg's libav header allocation mechanisms, creating a condition where maliciously crafted video content can trigger unexpected behavior in the application's memory management and rendering processes.
The technical root cause of this vulnerability lies in the improper handling of surface extents within the cairo graphics library when processing video frames through FFmpeg's multimedia framework. When Firefox encounters a crafted video file, the _cairo_surface_get_extents function fails to correctly coordinate with libav's header allocation routines in FFmpeg 0.10, leading to memory corruption or invalid memory access patterns. This misinteraction occurs during the video decoding and rendering process where Firefox attempts to determine the boundaries and dimensions of video surfaces, creating a scenario where the application's memory management becomes compromised. The vulnerability specifically affects Linux deployments where the combination of Firefox's graphics subsystem and FFmpeg's older header allocation mechanisms creates an exploitable condition that can be triggered remotely through web content.
The operational impact of CVE-2016-2839 extends beyond simple application instability, as remote attackers can leverage this weakness to systematically disrupt user experience and potentially create conditions for more sophisticated attacks. The denial of service achieved through this vulnerability can be executed without requiring user interaction beyond visiting a malicious webpage, making it particularly dangerous in web browsing contexts. Attackers can craft video content that when processed by the vulnerable Firefox versions will cause the browser to crash, potentially leading to complete application termination and requiring manual restart by users. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a specific case where improper memory handling in graphics rendering components creates exploitable conditions. The ATT&CK framework categorizes this as a denial of service attack vector under the technique of "Resource Exhaustion" where system resources are consumed in a way that renders the application non-functional.
Mitigation strategies for CVE-2016-2839 primarily focus on updating Firefox installations to versions that address the specific interaction issues between cairo and FFmpeg libraries. Users should immediately upgrade to Firefox 48.0 or later, or Firefox ESR 45.3 and subsequent releases that contain patches resolving the surface extents handling. System administrators should implement automated update mechanisms to ensure all Firefox installations remain current with security patches. Additionally, organizations may consider implementing web content filtering solutions that can detect and block potentially malicious video content, though this represents a secondary defense measure. The vulnerability demonstrates the importance of proper library coordination in multimedia applications and highlights how seemingly isolated component issues can create exploitable conditions in complex software ecosystems. Security monitoring should include detection of unusual browser crash patterns that may indicate exploitation attempts, while developers should review similar graphics library interactions to prevent analogous issues in other applications relying on similar multimedia frameworks.