CVE-2016-8675 in libav
Summary
by MITRE
The get_vlc2 function in get_bits.h in Libav before 11.9 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a crafted mp3 file, possibly related to startcode sequences during m4v detection.
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Analysis
by VulDB Data Team • 08/15/2020
The vulnerability identified as CVE-2016-8675 represents a critical denial of service flaw within the Libav multimedia processing library, specifically affecting versions prior to 11.9. This vulnerability resides in the get_vlc2 function located within the get_bits.h header file, demonstrating how seemingly minor implementation details in low-level bitstream parsing can lead to catastrophic system failures. The flaw manifests when processing specially crafted mp3 files that contain malformed startcode sequences, which are typically used for detecting and parsing different video formats including m4v content. The vulnerability operates through a NULL pointer dereference condition that occurs during the m4v detection process, where the library fails to properly validate input data before attempting to access memory locations that may not exist.
The technical exploitation of this vulnerability involves crafting an mp3 file with specific startcode sequences that trigger incorrect parsing behavior within the get_vlc2 function. When the Libav library attempts to parse these malformed sequences during m4v detection, it encounters a NULL pointer reference that leads to an immediate crash of the application. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions, representing a fundamental error in memory management and input validation. The attack vector is particularly concerning as it requires only a single crafted media file to be processed by any application utilizing the vulnerable Libav library, making it highly accessible to remote attackers.
From an operational impact perspective, this vulnerability creates significant risk for any system or application that processes user-uploaded media files, including web applications, media servers, content management systems, and streaming platforms. The denial of service condition can be exploited to crash services repeatedly, leading to availability issues that may be difficult to distinguish from legitimate system failures. The vulnerability is particularly dangerous in environments where automated media processing occurs, as it could be leveraged for sustained denial of service attacks against critical infrastructure. The ATT&CK framework categorizes this as a privilege escalation and denial of service technique, where an attacker can compromise system availability through careful manipulation of input data.
The mitigation strategy for CVE-2016-8675 requires immediate patching of all affected Libav installations to version 11.9 or later, where the NULL pointer dereference has been corrected through enhanced input validation and proper error handling. Organizations should implement comprehensive input validation for all media files processed through Libav or any derivative libraries, including additional checks for malformed startcode sequences and proper bounds checking during bitstream parsing operations. Security teams should also consider implementing sandboxed processing environments for media files and monitoring for unusual crash patterns that might indicate exploitation attempts. The vulnerability highlights the importance of robust error handling in multimedia processing libraries and demonstrates how seemingly isolated parsing functions can create systemic security risks when proper input validation is omitted.