CVE-2021-21835 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 decoding the atom associated with the “csgp” FOURCC 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 the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 08/29/2021
The vulnerability CVE-2021-21835 represents a critical integer overflow flaw within the GPAC Project Advanced Content library version 1.0.1, specifically affecting MPEG-4 decoding operations. This issue manifests when processing MPEG-4 files containing a specially crafted atom with the csgp FOURCC identifier, creating a dangerous condition that can lead to remote code execution. The vulnerability resides in the library's handling of file format parsing where unchecked arithmetic operations fail to validate input parameters before performing calculations that determine buffer allocation sizes.
The technical implementation of this flaw involves the manipulation of the csgp atom within MPEG-4 container format structures, where the decoder fails to properly validate the size parameters associated with this specific atom type. When an attacker crafts a malicious MPEG-4 file with oversized or malformed csgp atom data, the arithmetic operations used to calculate buffer sizes become overflowed, resulting in insufficient memory allocation for the subsequent buffer operations. This integer overflow condition directly translates into a heap-based buffer overflow scenario, where the program attempts to write beyond the allocated memory boundaries, causing memory corruption that can be exploited by malicious actors.
From an operational perspective, this vulnerability presents significant risk to end users who may encounter maliciously crafted media files through various attack vectors including email attachments, web downloads, or media streaming services that utilize the affected GPAC library. The exploitation requires only that a user open a specially crafted video file, making this a particularly dangerous vulnerability from a user interaction standpoint. The attack surface expands across all systems that depend on the GPAC library for multimedia processing, including media players, content management systems, and streaming applications that handle MPEG-4 formatted content.
The vulnerability maps directly to CWE-190, Integer Overflow or Wraparound, which specifically addresses issues where integer arithmetic operations produce results that exceed the maximum value representable by the data type. Additionally, this flaw aligns with ATT&CK technique T1203, Exploitation for Client Execution, as it enables remote code execution through client-side application processing of multimedia content. The heap-based buffer overflow component also connects to CWE-121, Stack-based Buffer Overflow, and CWE-122, Heap-based Buffer Overflow, though the specific implementation results in heap corruption rather than stack-based issues. Organizations should implement immediate mitigations including updating to patched versions of the GPAC library, implementing strict file format validation, and deploying sandboxing measures for media processing applications to prevent exploitation of this vulnerability across their networks and systems.