CVE-2021-32136 in GPAC
Summary
by MITRE • 09/13/2021
Heap buffer overflow in the print_udta function in MP4Box in GPAC 1.0.1 allows attackers to cause a denial of service or execute arbitrary code via a crafted file.
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Analysis
by VulDB Data Team • 03/05/2025
The vulnerability identified as CVE-2021-32136 represents a critical heap buffer overflow flaw within the MP4Box component of the GPAC multimedia framework version 1.0.1. This issue resides in the print_udta function which processes user data atoms within mp4 files, creating a potential attack surface where maliciously crafted media files could trigger unauthorized code execution or system denial of service. The flaw manifests when the application processes malformed udta atoms without proper bounds checking, allowing attackers to write beyond allocated heap memory regions.
The technical implementation of this vulnerability stems from inadequate input validation within the print_udta function where the application fails to properly verify the size and structure of user data atoms before attempting to process their contents. This oversight creates a condition where attacker-controlled data can overwrite adjacent memory locations, potentially corrupting heap metadata or executable code segments. The vulnerability is classified as a heap-based buffer overflow under CWE-122, which specifically addresses insufficient restriction of operations within the bounds of a memory buffer. The flaw occurs during the parsing phase of mp4 file structures where the application assumes valid data formats without adequate sanitization measures.
Operational impact assessment reveals that this vulnerability presents significant security risks to systems processing mp4 multimedia content through the GPAC framework. An attacker could leverage this flaw to execute arbitrary code with the privileges of the affected application, potentially leading to complete system compromise. The denial of service aspect affects availability by causing application crashes or system instability when processing malicious files, while the remote code execution capability enables persistent compromise of target systems. This vulnerability directly aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities for privilege escalation and persistent access, and T1059, covering command and scripting interpreter usage for code execution.
Mitigation strategies for CVE-2021-32136 should prioritize immediate patching of GPAC framework installations to version 1.0.2 or later where the buffer overflow has been addressed through proper bounds checking and input validation. Organizations should implement strict file validation procedures for mp4 content, particularly when processing user-uploaded or externally sourced media files. Network segmentation and application whitelisting can limit the attack surface by restricting access to vulnerable GPAC components. Additional defensive measures include implementing runtime protections such as heap randomization, stack canaries, and address space layout randomization to make exploitation more difficult. Regular security assessments should verify that no instances of the vulnerable GPAC version remain operational within the environment, while monitoring systems should be configured to detect anomalous behavior patterns consistent with buffer overflow exploitation attempts.