CVE-2021-21840 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 used to process an atom using the “saio” FOURCC code cause an integer overflow 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 vulnerability identified as CVE-2021-21840 represents a critical security flaw within the GPAC Project on Advanced Content library version 1.0.1, specifically affecting its MPEG-4 decoding capabilities. This integer overflow vulnerability stems from insufficient input validation during the processing of multimedia content, particularly when handling atoms with the specific FOURCC code "saio". The flaw exists within the library's handling of MPEG-4 container format elements, which are commonly used in video and audio streaming applications, making it a significant concern for multimedia software systems that rely on this library for content processing.
The technical implementation of this vulnerability involves unchecked arithmetic operations that occur when the library processes the saio atom within MPEG-4 files. This atom typically contains sample location information for audio and video samples, but the processing routine fails to validate the size calculations before performing arithmetic operations. When an attacker crafts a malicious MPEG-4 file with oversized or malformed saio atom values, the arithmetic operations overflow beyond the intended integer limits, creating a condition where heap memory allocation calculations become invalid. This leads to a heap-based buffer overflow scenario where the application attempts to write data beyond the allocated memory boundaries, resulting in memory corruption that can be exploited for arbitrary code execution.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it enables remote code execution capabilities that could be leveraged by attackers to compromise systems running applications that utilize the affected GPAC library. The vulnerability is particularly dangerous because it can be triggered simply by opening a malicious video file, making it an ideal candidate for phishing attacks or malicious content distribution through various digital channels. This exploitability profile aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute malicious code on target systems. The integer overflow condition creates a predictable memory corruption pattern that can be systematically exploited to overwrite critical memory structures, potentially leading to complete system compromise.
Mitigation strategies for CVE-2021-21840 should prioritize immediate patching of the GPAC library to version 1.0.2 or later, which contains the necessary fixes for the integer overflow vulnerability. Organizations should also implement content filtering mechanisms that validate MPEG-4 file structures before processing, particularly focusing on saio atom size calculations and implementing bounds checking for all arithmetic operations. Network security controls including web application firewalls and content inspection systems should be configured to block suspicious multimedia file types or those originating from untrusted sources. Additionally, system hardening measures such as heap protection mechanisms, address space layout randomization, and stack canaries should be enabled to reduce the effectiveness of potential exploitation attempts. The vulnerability's classification under CWE-190 - Integer Overflow or Wraparound indicates the need for comprehensive input validation and arithmetic operation safety checks throughout the library's multimedia processing pipeline, as outlined in the CWE guidelines for preventing integer overflow conditions that could lead to buffer overflows and memory corruption scenarios.