CVE-2017-16840 in FFmpeg
Summary
by MITRE
The VC-2 Video Compression encoder in FFmpeg 3.4 allows remote attackers to cause a denial of service (out-of-bounds read) because of incorrect buffer padding for non-Haar wavelets, related to libavcodec/vc2enc.c and libavcodec/vc2enc_dwt.c.
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Analysis
by VulDB Data Team • 01/11/2023
The vulnerability identified as CVE-2017-16840 represents a critical out-of-bounds read flaw within the VC-2 Video Compression encoder component of FFmpeg version 3.4. This issue specifically affects the handling of buffer padding during wavelet transform operations for non-Haar wavelets, creating a significant security risk that can be exploited remotely. The vulnerability resides in the libavcodec/vc2enc.c and libavcodec/vc2enc_dwt.c source files, which form the core of the video compression encoding functionality within the FFmpeg multimedia framework.
The technical flaw manifests when the encoder processes video content using non-Haar wavelets, which are mathematical functions employed in the discrete wavelet transform operations that underpin the VC-2 compression standard. During these operations, the encoder fails to properly account for buffer padding requirements, leading to memory access violations that occur beyond the allocated buffer boundaries. This incorrect buffer handling results in the program attempting to read memory locations that are either uninitialized, invalid, or not properly allocated, creating a predictable pattern of memory access errors that can be leveraged by malicious actors.
From an operational perspective, this vulnerability enables remote attackers to execute denial of service attacks against systems running vulnerable FFmpeg implementations. The out-of-bounds read condition can cause the encoder process to crash or behave unpredictably, effectively rendering the affected system unable to process video compression tasks. This type of vulnerability is particularly concerning in environments where FFmpeg serves as a backend component for video processing services, streaming platforms, or content management systems, as it can be exploited to disrupt legitimate service operations and potentially create opportunities for further exploitation attempts. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and can be categorized under ATT&CK technique T1499.004 for denial of service attacks.
The impact of this vulnerability extends beyond simple service disruption, as it represents a fundamental flaw in how the encoder handles memory operations during wavelet transform processing. Attackers can craft specially formatted video input that triggers the buffer overflow condition when processed by the vulnerable encoder, potentially causing system instability or complete application failure. This type of vulnerability is particularly dangerous in automated processing environments where FFmpeg is used to handle large volumes of incoming video content, as a single malicious input could cause cascading failures across multiple processing nodes. Mitigation strategies should focus on updating to patched versions of FFmpeg, implementing input validation controls, and deploying network-based protections that can detect and prevent exploitation attempts. The vulnerability demonstrates the importance of proper memory management and buffer boundary checking in multimedia processing libraries, particularly those handling complex mathematical operations like discrete wavelet transforms that require precise memory allocation and access patterns.