CVE-2016-6671 in FFmpeg
Summary
by MITRE
The raw_decode function in libavcodec/rawdec.c in FFmpeg before 3.1.2 allows remote attackers to cause a denial of service (memory corruption) or execute arbitrary code via a crafted SWF file.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2016-6671 represents a critical security flaw within the FFmpeg multimedia framework, specifically affecting the raw_decode function located in libavcodec/rawdec.c. This issue impacts versions of FFmpeg prior to 3.1.2 and demonstrates how multimedia processing libraries can become vectors for remote exploitation. The vulnerability manifests when processing specially crafted SWF (Shockwave Flash) files, which are widely used multimedia formats that can contain complex embedded content including video, audio, and interactive elements. SWF files are commonly encountered in web environments and are processed by various applications including web browsers, media players, and content management systems, making this vulnerability particularly dangerous as it can be triggered through routine media processing activities.
The technical nature of this vulnerability stems from improper input validation and memory handling within the raw decoding routine. When FFmpeg attempts to decode a malformed SWF file, the raw_decode function fails to properly validate buffer boundaries and memory allocation parameters, leading to memory corruption conditions that can result in either denial of service or arbitrary code execution. This type of vulnerability falls under the CWE-121 category of "Stack-based Buffer Overflow" and aligns with ATT&CK technique T1203 "Exploitation for Client Execution" as it enables remote code execution through client-side multimedia processing. The flaw occurs because the decoder does not adequately check the size and structure of incoming SWF data before attempting to process it, allowing attackers to craft malicious files that trigger buffer overflows or memory corruption during the decoding process.
The operational impact of CVE-2016-6671 extends far beyond simple denial of service scenarios, as it can enable complete system compromise when exploited. Attackers can leverage this vulnerability to execute arbitrary code on systems running affected versions of FFmpeg, potentially leading to full system compromise, data exfiltration, or lateral movement within network environments. The widespread adoption of FFmpeg across numerous applications, including content management systems, media servers, and web applications, means that exploitation can affect a broad range of targets. This vulnerability is particularly concerning in server environments where FFmpeg is used to process user-uploaded media files, as it creates an attack surface where untrusted input can be used to gain unauthorized access to systems. The vulnerability's remote exploitation capability means that attackers do not need physical access to target systems and can exploit it through web-based attacks, making it a significant threat to organizations that process multimedia content from untrusted sources.
Organizations should immediately update their FFmpeg installations to version 3.1.2 or later to remediate this vulnerability, as this represents the most effective mitigation strategy. Additionally, implementing input validation and sanitization measures for all multimedia content processed through FFmpeg can provide defense-in-depth protection. Security measures should include restricting SWF file processing capabilities, implementing proper memory protection mechanisms, and monitoring for unusual memory allocation patterns that might indicate exploitation attempts. The vulnerability highlights the importance of keeping multimedia processing libraries updated and demonstrates how seemingly benign media processing functions can become critical security risks when not properly secured against malformed input. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation, particularly in environments where FFmpeg is used for processing untrusted user content.