CVE-2018-6912 in FFmpeg
Summary
by MITRE
The decode_plane function in libavcodec/utvideodec.c in FFmpeg through 3.4.2 allows remote attackers to cause a denial of service (out of array read) via a crafted AVI file.
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Analysis
by VulDB Data Team • 02/06/2023
The vulnerability identified as CVE-2018-6912 represents a critical buffer over-read condition within the FFmpeg multimedia processing library, specifically affecting the decode_plane function in the utvideodec.c component. This flaw exists in FFmpeg versions through 3.4.2 and presents a significant security risk to systems that process multimedia content, particularly those handling AVI formatted files. The issue arises from inadequate input validation and boundary checking within the video decoding pipeline, creating an exploitable condition that can be triggered through maliciously crafted media files.
The technical implementation of this vulnerability stems from insufficient bounds checking during the decoding process of UTVideo compressed video streams. When FFmpeg encounters a specially crafted AVI file containing malformed video data, the decode_plane function fails to properly validate array access boundaries before reading video plane data. This allows attackers to manipulate the decoding process such that memory locations beyond the allocated array boundaries are accessed, resulting in an out-of-bounds read operation. The vulnerability falls under the CWE-125 weakness category, which specifically addresses out-of-bounds read conditions that can lead to information disclosure, system instability, or potential privilege escalation depending on the execution context.
From an operational perspective, this vulnerability enables remote attackers to execute denial of service attacks against systems running vulnerable versions of FFmpeg. The out-of-bounds read condition typically results in application crashes or system instability, effectively preventing legitimate users from accessing multimedia content. The impact extends beyond simple service disruption as this vulnerability can be exploited in web applications, media processing servers, and content delivery networks that rely on FFmpeg for video handling. Attackers can craft malicious AVI files that, when processed by vulnerable systems, will cause the decoding process to fail and potentially expose system memory contents through the memory access violations.
The exploitation of CVE-2018-6912 aligns with several tactics outlined in the MITRE ATT&CK framework, particularly those related to privilege escalation and denial of service operations. This vulnerability can be classified under the T1499.004 technique for unauthorized access to system resources through memory corruption attacks. The attack surface includes any application or service that utilizes FFmpeg for video processing, including web browsers, media servers, streaming platforms, and content management systems. Organizations using FFmpeg in their multimedia processing pipelines face significant risk exposure, as the vulnerability can be triggered through simple file uploads or streaming operations without requiring user interaction or elevated privileges.
Mitigation strategies for this vulnerability require immediate patching of FFmpeg installations to versions 3.4.3 or later, where the buffer over-read condition has been addressed through proper boundary validation and input sanitization. System administrators should implement comprehensive monitoring for unauthorized file uploads and processing of multimedia content, particularly in web applications that accept user-generated media. Network segmentation and application whitelisting can help reduce the attack surface by limiting access to vulnerable FFmpeg processing components. Additionally, organizations should conduct regular vulnerability assessments and penetration testing to identify other potential exploitation vectors within their multimedia processing infrastructure. The fix implemented by the FFmpeg development team involved strengthening the input validation mechanisms within the decode_plane function to ensure proper bounds checking before array access operations, effectively preventing the out-of-bounds read condition that previously enabled denial of service attacks.