CVE-2020-21066 in Bento4
Summary
by MITRE • 08/14/2021
An issue was discovered in Bento4 v1.5.1.0. There is a heap-buffer-overflow in AP4_Dec3Atom::AP4_Dec3Atom at Ap4Dec3Atom.cpp, leading to a denial of service (program crash), as demonstrated by mp42aac.
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Analysis
by VulDB Data Team • 08/18/2021
The vulnerability CVE-2020-21066 represents a critical heap buffer overflow condition within the Bento4 multimedia framework version 1.5.1.0. This issue specifically affects the AP4_Dec3Atom::AP4_Dec3Atom constructor function located in the Ap4Dec3Atom.cpp source file. The flaw manifests when processing mp42aac tool inputs, which are used for converting mp4 files to aac format, making it particularly concerning for multimedia processing applications that handle various audio formats.
The technical nature of this vulnerability stems from improper input validation and memory management within the audio atom parsing mechanism of the Bento4 library. When the system attempts to parse certain malformed or specially crafted mp4 files containing DEC3 atoms, the AP4_Dec3Atom constructor fails to properly bounds-check memory allocations, leading to a heap buffer overflow condition. This occurs because the code does not adequately validate the size or structure of incoming audio metadata, allowing an attacker to provide malicious input that exceeds allocated buffer boundaries. The vulnerability is classified as a heap-based buffer overflow under CWE-121, which represents a fundamental memory safety issue where data written beyond allocated heap memory regions can corrupt adjacent memory locations.
The operational impact of this vulnerability extends beyond simple program crashes, presenting significant risks to multimedia processing systems that rely on Bento4 for audio format conversion and manipulation. When exploited, the heap buffer overflow causes the affected application to terminate abruptly, resulting in denial of service conditions that can disrupt legitimate user workflows and automated processing pipelines. In environments where mp42aac is used for batch processing or automated content conversion, such as media servers, content management systems, or digital asset management platforms, this vulnerability can lead to complete service disruption. The crash occurs during the parsing phase of audio atom processing, meaning that any application utilizing Bento4 for mp4 file analysis or conversion becomes vulnerable to this attack vector, potentially affecting a wide range of multimedia applications and services.
Mitigation strategies for CVE-2020-21066 should prioritize immediate software updates to versions that have addressed this heap buffer overflow vulnerability. System administrators and developers should implement input validation measures that restrict or sanitize mp4 file inputs before processing, particularly focusing on audio atom structures that could trigger the vulnerable code path. The ATT&CK framework categorizes this type of vulnerability under T1203 - Exploitation for Client Execution, where attackers may leverage buffer overflow conditions to disrupt services or potentially escalate privileges. Additionally, implementing memory safety techniques such as address sanitizer instrumentation, stack canaries, and heap integrity checks can provide additional protection layers. Organizations should also consider network segmentation and access controls to limit exposure of systems running vulnerable versions of Bento4, particularly those handling untrusted multimedia content. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of the vulnerable library version within the organization's infrastructure.