CVE-2017-9996 in FFmpeg
Summary
by MITRE
The cdxl_decode_frame function in libavcodec/cdxl.c in FFmpeg 2.8.x before 2.8.12, 3.0.x before 3.0.8, 3.1.x before 3.1.8, 3.2.x before 3.2.5, and 3.3.x before 3.3.1 does not exclude the CHUNKY format, which allows remote attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via a crafted file.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability identified as CVE-2017-9996 represents a critical heap-based buffer overflow in the FFmpeg multimedia framework affecting multiple version ranges. This issue resides within the cdxl_decode_frame function located in libavcodec/cdxl.c, which processes CDXL (Commodore Digital eXtension Library) video format files. The flaw specifically manifests when the decoder fails to properly validate or exclude the CHUNKY format during frame decoding operations, creating a dangerous condition that can be exploited remotely through maliciously crafted media files.
The technical implementation of this vulnerability stems from insufficient input validation within the CDXL decoder component. When processing files that contain the CHUNKY format specification, the function does not adequately check format parameters before attempting to allocate memory or copy data into buffers. This oversight allows attackers to craft specially designed CDXL files that trigger memory corruption during the decoding process. The vulnerability maps to CWE-121, heap-based buffer overflow, where the attacker can manipulate the heap memory layout through controlled input data, potentially leading to application crashes or more severe consequences depending on the execution environment.
The operational impact of CVE-2017-9996 extends beyond simple denial of service scenarios, as the vulnerability could enable remote code execution in certain configurations. When exploited, the heap overflow can cause applications using FFmpeg to crash unpredictably, consuming system resources and potentially allowing attackers to execute arbitrary code with the privileges of the affected application. This makes the vulnerability particularly dangerous in server environments where FFmpeg is used for media processing, streaming platforms, or content management systems. The attack vector is remote and requires no authentication, making it accessible to anyone capable of delivering a malicious file to a vulnerable system.
Security practitioners should implement immediate mitigations including updating to the patched versions of FFmpeg where CVE-2017-9996 has been resolved. The affected versions include FFmpeg 2.8.x before 2.8.12, 3.0.x before 3.0.8, 3.1.x before 3.1.8, 3.2.x before 3.2.5, and 3.3.x before 3.3.1. Organizations should also consider implementing network-based detection mechanisms to identify and block suspicious media file transfers, particularly those with CDXL format extensions. Additionally, application developers should ensure proper input validation and memory management practices are implemented when integrating FFmpeg libraries, following ATT&CK technique T1203 for process injection prevention and T1059 for command and scripting interpreter defenses. The vulnerability demonstrates the critical importance of robust input validation in multimedia processing libraries and highlights the need for comprehensive security testing of codec implementations.