CVE-2012-0851 in libav
Summary
by MITRE
The ff_h264_decode_seq_parameter_set function in h264_ps.c in libavcodec in FFmpeg before 0.9.1 and in Libav 0.5.x before 0.5.9, 0.6.x before 0.6.6, 0.7.x before 0.7.6, and 0.8.x before 0.8.3 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a crafted H.264 file, related to the chroma_format_idc value.
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Analysis
by VulDB Data Team • 12/08/2021
The vulnerability identified as CVE-2012-0851 represents a critical security flaw in the FFmpeg multimedia framework's H.264 video decoding implementation. This vulnerability affects multiple versions of both FFmpeg and its fork Libav, specifically targeting the ff_h264_decode_seq_parameter_set function located in the h264_ps.c file. The flaw manifests when processing specially crafted H.264 video files that contain malformed chroma_format_idc values, which are essential components of the H.264 video stream specification used for defining color sampling formats.
The technical nature of this vulnerability stems from inadequate input validation within the H.264 parameter set decoding process. When the decoder encounters a chroma_format_idc value that exceeds expected boundaries or violates the H.264 specification constraints, the decoding function fails to properly handle the malformed data. This leads to memory corruption issues that can result in application crashes or potentially allow for arbitrary code execution. The vulnerability specifically exploits the way the decoder processes the chroma_format_idc field, which defines how chrominance samples are sampled relative to luminance samples in the video stream. According to CWE-125, this represents an out-of-bounds read condition that can escalate to more severe security implications.
The operational impact of CVE-2012-0851 extends beyond simple denial of service scenarios, as it can potentially enable remote code execution attacks. Attackers can craft malicious H.264 files that, when processed by vulnerable applications, will trigger the buffer overflow condition. This vulnerability affects a wide range of software systems that rely on FFmpeg or Libav for video processing, including media players, streaming servers, and content management systems. The attack surface is particularly broad since H.264 is one of the most widely used video codecs in digital media applications, making this vulnerability highly exploitable across numerous platforms and services. The vulnerability aligns with ATT&CK technique T1203, which involves the exploitation of input validation flaws to achieve code execution in multimedia processing applications.
Mitigation strategies for CVE-2012-0851 primarily involve immediate software updates to patched versions of FFmpeg and Libav. Organizations should prioritize updating to FFmpeg 0.9.1 or later, and Libav versions 0.5.9, 0.6.6, 0.7.6, and 0.8.3 or later to address this vulnerability. Additionally, implementing input validation measures at the application level can provide defense-in-depth protection, particularly when processing untrusted video content. Network administrators should consider implementing content filtering mechanisms that scan video files for potentially malicious H.264 structures before they reach end-user applications. The vulnerability highlights the importance of proper bounds checking in multimedia codec implementations and demonstrates how seemingly minor input validation gaps can result in significant security risks. Security teams should also monitor for similar vulnerabilities in other multimedia libraries and ensure comprehensive testing of media processing pipelines to prevent similar issues from occurring in the future.