CVE-2012-0856 in FFmpeg
Summary
by MITRE
Heap-based buffer overflow in the MPV_frame_start function in libavcodec/mpegvideo.c in FFmpeg before 0.9.1, when the lowres option is enabled, allows remote attackers to cause a denial of service (application crash) via a crafted H263 media file. NOTE: this vulnerability exists because of a regression error.
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability CVE-2012-0856 represents a heap-based buffer overflow in the FFmpeg multimedia framework that specifically affects the MPV_frame_start function within the libavcodec/mpegvideo.c source file. This critical security flaw was discovered in FFmpeg versions prior to 0.9.1 and stems from a regression error that reintroduced an existing vulnerability pattern. The vulnerability manifests when the lowres option is enabled during video processing, creating a dangerous condition where remote attackers can craft malicious H263 media files to exploit this weakness. The root cause lies in improper input validation and memory management within the video decoding pipeline, where the application fails to properly bounds-check data when processing video frames under low resolution settings.
The technical exploitation of this vulnerability occurs through a carefully crafted H263 video file that triggers an overflow in the heap memory allocation used by the MPV_frame_start function. When FFmpeg processes such malicious media content with the lowres option activated, the application allocates insufficient memory buffers to accommodate the expected video frame data, resulting in memory corruption that leads to application instability. This heap-based overflow specifically targets the memory management system of FFmpeg's video decoding component, where the frame start processing function does not adequately validate the size parameters of incoming video data. The vulnerability's classification as a regression error indicates that this was a previously identified weakness that was inadvertently reintroduced during code modifications or updates to the FFmpeg library.
The operational impact of CVE-2012-0856 extends beyond simple denial of service, as it represents a significant threat to multimedia processing applications that rely on FFmpeg for video handling. Remote attackers can leverage this vulnerability to cause application crashes, potentially leading to service disruption for streaming platforms, video processing servers, and multimedia applications that utilize FFmpeg as their core decoding engine. The vulnerability affects any system that processes H263 video content with low resolution enabled, making it particularly dangerous in environments where untrusted media files are processed automatically. This includes web applications, media servers, content delivery networks, and any software that accepts user-uploaded video content without proper validation, as the exploitation can occur without requiring user interaction or specific privileges.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions where insufficient memory is allocated for data that exceeds the allocated buffer size. From an adversarial perspective, this weakness maps to ATT&CK technique T1203, which involves the exploitation of software vulnerabilities to cause system instability or crashes. Organizations using FFmpeg in their multimedia processing pipelines should prioritize immediate patching to version 0.9.1 or later, as this vulnerability can be exploited remotely without authentication. Mitigation strategies include disabling the lowres option in applications that process untrusted video content, implementing strict input validation for video files, and monitoring for unusual application crashes or memory allocation patterns. The regression nature of this vulnerability underscores the importance of thorough testing and quality assurance processes during software updates to prevent previously resolved security issues from reoccurring in newer versions of multimedia frameworks.