CVE-2016-7502 in FFmpeg
Summary
by MITRE
The cavs_idct8_add_c function in libavcodec/cavsdsp.c in FFmpeg before 3.1.4 is vulnerable to reading out-of-bounds memory when decoding with cavs_decode.
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Analysis
by VulDB Data Team • 07/15/2019
The vulnerability identified as CVE-2016-7502 represents a critical memory safety issue within the FFmpeg multimedia framework that affects versions prior to 3.1.4. This flaw resides in the cavs_idct8_add_c function located within the libavcodec/cavsdsp.c source file, specifically manifesting during the decoding process of cavs_decode operations. The vulnerability stems from inadequate bounds checking mechanisms that fail to validate memory access patterns when processing certain compressed video streams, creating a potential pathway for malicious actors to exploit memory corruption behaviors.
The technical implementation of this vulnerability demonstrates a classic out-of-bounds memory read condition that occurs when the cavs_idct8_add_c function processes inverse discrete cosine transform operations on video data. This function operates within the context of the Chinese AVS (Audio Video Standard) decoding pipeline, where it handles the reconstruction of 8x8 pixel blocks from frequency domain coefficients. When malformed or specially crafted video streams are processed, the function fails to properly validate array indices or buffer boundaries, allowing subsequent memory access operations to read data beyond the allocated memory regions. This behavior aligns with CWE-129, which categorizes improper validation of array indices as a fundamental flaw in input handling, and specifically relates to CWE-787, which addresses out-of-bounds write operations that can lead to information disclosure or code execution.
The operational impact of this vulnerability extends across numerous digital media applications that rely on FFmpeg for video processing and playback functionality. Systems utilizing affected versions of FFmpeg become susceptible to memory corruption attacks that could result in application crashes, denial of service conditions, or potentially more severe outcomes including arbitrary code execution. The vulnerability affects not only standalone media players but also web browsers, content management systems, streaming platforms, and other applications that incorporate FFmpeg as a core component for multimedia processing. Attackers could leverage this weakness by crafting malicious video files that trigger the vulnerable code path during normal playback operations, potentially leading to system compromise or service disruption. This vulnerability particularly impacts environments where users might encounter untrusted video content, as the decoding process could be initiated automatically during content delivery or user interaction scenarios.
Mitigation strategies for CVE-2016-7502 primarily focus on immediate version upgrades to FFmpeg 3.1.4 or later, which contain the necessary patches to address the out-of-bounds memory read condition. Organizations should prioritize updating their FFmpeg installations across all affected systems, including servers, desktop applications, and mobile platforms that process video content. Additionally, implementing input validation measures and content filtering mechanisms can provide defensive layers against exploitation attempts, though these should not be considered replacements for the official patches. Security teams should monitor for additional related vulnerabilities in the FFmpeg codebase and consider implementing runtime protections such as address space layout randomization and stack canaries to reduce the effectiveness of potential exploitation attempts. The vulnerability also highlights the importance of maintaining up-to-date multimedia libraries and implementing comprehensive security testing procedures for third-party components used in media processing pipelines, as outlined in ATT&CK framework's T1068, which addresses local privilege escalation through software vulnerabilities.