CVE-2018-20409 in Bento4
Summary
by MITRE
An issue was discovered in Bento4 1.5.1-627. There is a heap-based buffer over-read in AP4_AvccAtom::Create in Core/Ap4AvccAtom.cpp, as demonstrated by mp42hls.
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Analysis
by VulDB Data Team • 06/20/2023
The vulnerability identified as CVE-2018-20409 affects Bento4 version 1.5.1-627 and represents a critical heap-based buffer over-read condition within the AP4_AvccAtom::Create function located in Core/Ap4AvccAtom.cpp. This issue manifests when processing media files through the mp42hls utility, which is part of the Bento4 multimedia framework used for creating and manipulating mp4 files. The flaw occurs during the parsing of AVC (Advanced Video Coding) configuration atoms within mp4 containers, specifically when handling the sequence parameter set (SPS) and picture parameter set (PPS) data structures that define video codec parameters.
The technical implementation of this vulnerability stems from inadequate bounds checking during the parsing of AVC configuration data within the mp4 container format. When the AP4_AvccAtom::Create function processes incoming data, it fails to properly validate the size and structure of the incoming AVC configuration information, particularly in the sequence parameter set data. This allows an attacker to craft malicious mp4 files that contain oversized or malformed SPS data structures, causing the application to read memory beyond the allocated buffer boundaries. The heap-based nature of this over-read means that the application accesses memory locations that were not properly allocated for the intended data structure, potentially leading to information disclosure or application instability.
The operational impact of this vulnerability extends beyond simple crash conditions, as it can be exploited to extract sensitive memory contents from the application process or potentially enable further exploitation techniques. Attackers could leverage this vulnerability by crafting specially formatted mp4 files that, when processed by applications using Bento4 libraries, would trigger the buffer over-read condition. This could result in information disclosure attacks where adjacent memory contents are read and potentially exfiltrated, or in more severe cases, could provide a foundation for privilege escalation or remote code execution depending on the application context and memory layout. The vulnerability affects any system that utilizes Bento4 for mp4 file processing, particularly media servers, content delivery networks, and applications that handle user-uploaded video content.
Mitigation strategies for CVE-2018-20409 should focus on immediate patching of affected Bento4 installations to version 1.5.1-628 or later, which contains the necessary bounds checking fixes. Organizations should also implement input validation measures for any mp4 files processed through Bento4-based applications, including size and format validation before file processing. Network-level defenses should include content inspection systems that can detect and block malformed mp4 files, particularly those with suspiciously large SPS structures. From a defensive perspective, this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and may be categorized under ATT&CK technique T1059 for command and scripting interpreter usage, as attackers might leverage information disclosure from such vulnerabilities to plan further attacks. The fix implemented by the Bento4 team involves strengthening the buffer validation logic within the AP4_AvccAtom::Create function to properly validate the size of incoming AVC configuration data before attempting to read from the buffer, preventing the heap-based over-read condition from occurring.