CVE-2018-20095 in Bento4
Summary
by MITRE
An issue was discovered in EnsureCapacity in Core/Ap4Array.h in Bento4 1.5.1-627. Crafted MP4 input triggers an attempt at excessive memory allocation, as demonstrated by mp42hls.
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Analysis
by VulDB Data Team • 06/18/2023
The vulnerability identified as CVE-2018-20095 resides within the Bento4 media processing library version 1.5.1-627, specifically in the EnsureCapacity function located in Core/Ap4Array.h. This issue represents a classic memory allocation flaw that can be exploited through carefully crafted MP4 media files. The vulnerability manifests when the mp42hls utility processes malformed input files, triggering an excessive memory allocation attempt that can lead to resource exhaustion and potential system instability. The flaw demonstrates characteristics of a buffer over-allocation condition where the application fails to properly validate input parameters before attempting to allocate memory resources.
From a technical perspective, the vulnerability stems from inadequate input validation within the array capacity management system. When the EnsureCapacity function processes MP4 metadata structures, it does not properly constrain the memory allocation requests based on the actual size requirements of the input data. This allows an attacker to craft MP4 files containing maliciously inflated size indicators that cause the application to attempt allocating memory in quantities that far exceed what is reasonable for the actual data content. The flaw operates at the intersection of media file parsing and memory management, where the parser's trust in metadata fields leads to unbounded memory allocation requests. This type of vulnerability falls under CWE-704, which covers improper type conversion or cast operations, and more specifically relates to CWE-122, which addresses insufficient checking of heap buffer bounds.
The operational impact of this vulnerability extends beyond simple denial of service conditions. When exploited, the excessive memory allocation can cause the mp42hls utility to consume all available system memory, leading to system instability, application crashes, or even complete system hangs. In environments where Bento4 libraries are used for media processing, this vulnerability can be particularly dangerous as it allows attackers to consume system resources through legitimate media processing workflows. The vulnerability is especially concerning in automated processing environments or web applications that accept user-uploaded MP4 files, where an attacker could systematically exhaust system resources by uploading maliciously crafted media files. This type of attack aligns with ATT&CK technique T1499.001, which covers resource exhaustion attacks targeting memory resources.
Mitigation strategies for CVE-2018-20095 should focus on implementing robust input validation and memory allocation limits within the Bento4 library. The primary fix involves adding bounds checking to the EnsureCapacity function to prevent allocation requests that exceed reasonable thresholds based on the actual input file size and structure. Organizations should upgrade to patched versions of Bento4 where the vulnerability has been addressed through proper input validation mechanisms. Additionally, implementing memory allocation limits and monitoring within applications that use Bento4 can provide additional defense in depth. System administrators should also consider implementing file size limits and content validation for MP4 files processed through these utilities. The vulnerability highlights the importance of secure coding practices in media processing libraries, particularly around memory management and input validation, as outlined in secure coding guidelines such as those provided by the CERT/CC Secure Coding Standards.