CVE-2014-9317 in FFMpeg
Summary
by MITRE
The decode_ihdr_chunk function in libavcodec/pngdec.c in FFMpeg before 2.1.6, 2.2.x through 2.3.x, and 2.4.x before 2.4.4 allows remote attackers to cause a denial of service (out-of-bounds heap access) and possibly have other unspecified impact via an IDAT before an IHDR in a PNG file.
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Analysis
by VulDB Data Team • 04/07/2022
The vulnerability identified as CVE-2014-9317 represents a critical heap-based buffer overflow condition within the FFmpeg multimedia framework's PNG decoding component. This flaw exists in the decode_ihdr_chunk function located in libavcodec/pngdec.c, affecting multiple versions of FFmpeg including those before 2.1.6, 2.2.x through 2.3.x, and 2.4.x before 2.4.4. The vulnerability stems from improper handling of PNG file structures where the decoder fails to properly validate the order and content of PNG chunks, specifically when an IDAT chunk appears before an IHDR chunk in the file structure.
The technical implementation of this vulnerability exploits the inherent assumptions made by the PNG decoder about the sequential ordering of chunks within a PNG file. In standard PNG format, the IHDR chunk must appear first to define the image header information including width, height, and color type. However, the vulnerable FFmpeg implementation does not adequately validate this ordering requirement, allowing maliciously crafted PNG files to place IDAT chunks before IHDR chunks. When the decode_ihdr_chunk function processes such malformed input, it attempts to read header information from memory locations that have not been properly initialized or allocated, resulting in out-of-bounds heap access patterns.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more severe security consequences. While the primary effect manifests as heap corruption leading to application crashes and denial of service conditions, the out-of-bounds memory access pattern creates opportunities for attackers to potentially execute arbitrary code or manipulate program execution flow. This represents a classic buffer overflow scenario that can be leveraged for privilege escalation or remote code execution depending on the execution context. The vulnerability aligns with CWE-121, heap-based buffer overflow, and demonstrates characteristics consistent with ATT&CK technique T1203 for legitimate program exploitation through memory corruption.
The exploitation of this vulnerability requires an attacker to craft a malicious PNG file that violates the standard PNG specification by placing IDAT chunks before IHDR chunks. When a vulnerable FFmpeg application processes this malformed file, the decode_ihdr_chunk function attempts to parse the header information from an uninitialized or improperly allocated memory region. This creates a scenario where the application may read from or write to memory locations outside the intended heap allocation boundaries, potentially causing unpredictable behavior including application crashes, data corruption, or in worst-case scenarios, code execution.
Mitigation strategies for CVE-2014-9317 primarily focus on updating to patched versions of FFmpeg where the PNG decoding logic has been corrected to properly validate chunk ordering and memory allocation. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing FFmpeg for multimedia processing are updated to versions 2.1.6 or later for the 2.1.x branch, 2.3.4 or later for the 2.2.x and 2.3.x branches, and 2.4.4 or later for the 2.4.x branch. Additionally, input validation should be implemented at the application level to filter PNG files before processing, particularly when dealing with untrusted user uploads or third-party content. Network-based protections such as web application firewalls can also be configured to detect and block suspicious PNG file patterns, though the most effective mitigation remains the application of vendor-provided security patches.