CVE-2017-17128 in libav
Summary
by MITRE
The h264_slice_init function in libavcodec/h264_slice.c in Libav 12.2 allows remote attackers to cause a denial of service (segmentation fault and application crash) via a crafted file.
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Analysis
by VulDB Data Team • 12/12/2019
The vulnerability identified as CVE-2017-17128 resides within the Libav multimedia framework, specifically in the h264_slice_init function located in libavcodec/h264_slice.c. This critical flaw affects Libav version 12.2 and represents a denial of service vulnerability that can be exploited remotely through maliciously crafted media files. The issue manifests when the application processes specially constructed h264 video content that triggers a segmentation fault, leading to application crashes and system instability. The vulnerability demonstrates a classic buffer over-read condition where the function fails to properly validate input parameters during video slice initialization, creating an exploitable condition that can be leveraged by attackers to disrupt service availability.
The technical implementation of this vulnerability stems from inadequate input validation within the H.264 video decoding pipeline. When the h264_slice_init function processes malformed video data, it fails to properly bounds-check array accesses or validate slice header parameters, resulting in memory access violations that cause segmentation faults. This flaw operates at the intersection of multimedia processing and memory safety, where the decoding logic does not adequately handle edge cases or malformed input streams. The vulnerability is classified under CWE-125 as an out-of-bounds read condition, where the application attempts to access memory beyond the allocated buffer boundaries. The specific nature of the flaw allows attackers to craft video files with malicious slice headers that cause the decoder to attempt invalid memory operations, leading to immediate application termination and system instability.
From an operational perspective, this vulnerability presents significant risk to systems that process or stream H.264 video content, particularly in environments where users can upload or download media files. The impact extends beyond simple service disruption to potentially affect critical infrastructure, streaming services, web applications, and media processing platforms that rely on Libav for video handling. Attackers can exploit this vulnerability to cause denial of service against media servers, content management systems, or any application that utilizes Libav for video decoding operations. The remote exploitation capability means that malicious actors can trigger crashes without requiring local access, making this vulnerability particularly dangerous in web-facing applications or services that process untrusted media content. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, where adversaries leverage software flaws to disrupt services through crafted input data.
Mitigation strategies for CVE-2017-17128 require immediate implementation of software updates and patches from Libav maintainers, as the vulnerability exists in version 12.2 and has been addressed in subsequent releases. Organizations should prioritize patching affected systems and implementing input validation measures to prevent malformed video files from reaching the vulnerable decoding functions. Additional defensive measures include deploying network-based intrusion detection systems to monitor for suspicious media file patterns, implementing strict content filtering for uploaded media, and establishing robust input sanitization processes for all video processing pipelines. The vulnerability highlights the importance of proper memory management and input validation in multimedia processing libraries, emphasizing that security considerations must be integrated throughout the software development lifecycle. System administrators should also consider implementing application-level sandboxing or containerization for media processing components to limit the impact of potential exploitation attempts and provide additional layers of defense against similar vulnerabilities.