CVE-2021-21842 in Advanced Content
Summary
by MITRE • 08/25/2021
An exploitable integer overflow vulnerability exists within the MPEG-4 decoding functionality of the GPAC Project on Advanced Content library v1.0.1. A specially crafted MPEG-4 input can cause an integer overflow when processing an atom using the 'ssix' FOURCC code, due to unchecked arithmetic resulting in a heap-based buffer overflow that causes memory corruption. An attacker can convince a user to open a video to trigger this vulnerability.
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Analysis
by VulDB Data Team • 08/29/2021
The CVE-2021-21842 vulnerability represents a critical integer overflow flaw within the GPAC Project Advanced Content library version 1.0.1 that specifically impacts MPEG-4 decoding operations. This vulnerability resides in the library's handling of atom processing with the 'ssix' FOURCC code, which is a fundamental component of the MPEG-4 file format structure. The issue manifests when the library processes specially crafted MPEG-4 files that contain maliciously constructed atom data, creating a dangerous condition where unchecked arithmetic operations lead to predictable memory corruption patterns. The vulnerability operates at the intersection of multimedia processing and memory safety, making it particularly dangerous in environments where users might encounter untrusted video content from various sources.
The technical exploitation of this vulnerability follows a well-defined pattern of integer arithmetic failure that ultimately results in heap-based buffer overflow conditions. When the GPAC library encounters an MPEG-4 file with the specific 'ssix' atom structure, it performs calculations to determine buffer sizes for memory allocation without proper validation of the arithmetic results. This unchecked arithmetic allows an attacker to manipulate the size parameters in such a way that the resulting buffer allocation becomes insufficient for the actual data processing requirements, creating a condition where subsequent memory writes overflow into adjacent memory regions. The vulnerability maps directly to CWE-190, which specifically addresses integer overflow conditions, and more broadly aligns with CWE-121, heap-based buffer overflow scenarios, making it a prime target for exploitation within the context of multimedia processing applications.
The operational impact of this vulnerability extends far beyond simple memory corruption, as it provides attackers with potential code execution capabilities through carefully crafted malicious video files. Modern exploitation techniques leverage such buffer overflow conditions to manipulate program execution flow, potentially allowing attackers to execute arbitrary code with the privileges of the affected application. The vulnerability's trigger mechanism is particularly concerning because it requires only user interaction through opening a video file, making it highly suitable for social engineering campaigns where users might be tricked into viewing malicious content from seemingly legitimate sources. This attack vector aligns with ATT&CK technique T1203, which covers legitimate user interaction, and demonstrates how multimedia applications can serve as effective attack surfaces for privilege escalation and persistent threats.
Mitigation strategies for CVE-2021-21842 must address both immediate remediation and long-term architectural improvements in the affected GPAC library. The primary solution involves updating to the patched version of the GPAC Project Advanced Content library where the integer overflow has been corrected through proper bounds checking and arithmetic validation. Organizations should implement strict input validation procedures for all multimedia content processing, including automatic scanning for malformed atom structures and implementing memory protection mechanisms such as stack canaries and address space layout randomization. Additionally, security teams should establish monitoring protocols for detecting unusual memory allocation patterns that might indicate exploitation attempts, while maintaining comprehensive network segmentation to limit the potential impact of successful attacks. The vulnerability underscores the importance of robust input validation in multimedia processing libraries and serves as a reminder of the critical security considerations necessary when handling untrusted binary content in media applications.