CVE-2021-21841 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 when reading an atom using the 'sbgp' FOURCC code can 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.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/29/2021
The vulnerability CVE-2021-21841 represents a critical security flaw within the GPAC Project Advanced Content library version 1.0.1, specifically targeting its MPEG-4 decoding capabilities. This issue manifests as an exploitable integer overflow that occurs during the processing of multimedia content, making it particularly dangerous for applications that handle user-provided video files. The vulnerability resides in how the library processes specific atom structures within MPEG-4 files, particularly those identified by the 'sbgp' FOURCC code, which is used to define sample grouping information in the multimedia container format.
The technical implementation of this vulnerability stems from unchecked arithmetic operations within the decoding routine that processes the 'sbgp' atom. When a maliciously crafted MPEG-4 file contains specially constructed data within this atom, the library performs integer arithmetic operations without proper validation of overflow conditions. This unchecked arithmetic leads to an integer overflow that subsequently causes a heap-based buffer overflow, resulting in memory corruption that can be exploited by attackers. The vulnerability demonstrates characteristics consistent with CWE-190, which identifies integer overflow conditions, and CWE-121, which addresses stack-based buffer overflow issues. The flaw occurs because the application fails to validate input parameters before performing calculations that determine buffer allocation sizes, creating a scenario where attacker-controlled data can manipulate memory layout.
The operational impact of this vulnerability extends beyond simple code execution, as it can be triggered through normal user interaction with multimedia content. An attacker can craft a malicious video file that, when opened by an application using the vulnerable GPAC library, will automatically trigger the integer overflow condition. This makes the vulnerability particularly dangerous in environments where users might encounter untrusted video content, such as web browsers, media players, or content management systems. The heap-based buffer overflow creates opportunities for memory corruption that can potentially lead to arbitrary code execution, making this a severe threat to system security. The vulnerability affects any application that relies on the GPAC library for MPEG-4 video processing, including multimedia frameworks, streaming applications, and content delivery platforms.
Mitigation strategies for CVE-2021-21841 should prioritize immediate patching of the GPAC library to version 1.0.2 or later, which contains the necessary fixes for the integer overflow conditions. Organizations should implement defensive programming practices such as input validation and bounds checking for all multimedia file processing operations, particularly those involving variable-length data structures. Security teams should consider deploying runtime protections such as address space layout randomization and stack canaries to mitigate exploitation attempts. The vulnerability aligns with ATT&CK technique T1203, which involves exploitation of software vulnerabilities, and T1059, which addresses execution through command and scripting interpreters. Additionally, network segmentation and content filtering mechanisms should be implemented to prevent untrusted multimedia content from reaching systems that utilize the vulnerable library, reducing the attack surface and providing additional layers of defense against potential exploitation attempts.