CVE-2019-20631 in GPAC
Summary
by MITRE
An issue was discovered in libgpac.a in GPAC before 0.8.0, as demonstrated by MP4Box. It contains an invalid pointer dereference in gf_list_count in utils/list.c that can cause a denial of service via a crafted MP4 file.
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Analysis
by VulDB Data Team • 05/11/2025
The vulnerability identified as CVE-2019-20631 represents a critical denial of service flaw within the GPAC multimedia framework, specifically affecting versions prior to 0.8.0. This issue manifests in the libgpac.a library component, which is widely utilized for multimedia processing and file format handling. The vulnerability is particularly concerning as it affects the MP4Box utility, a core component of GPAC used for manipulating and converting multimedia files, making it a potential target for attackers seeking to disrupt multimedia processing workflows.
The technical root cause of this vulnerability lies within the gf_list_count function located in the utils/list.c file of the GPAC library. This function is responsible for counting elements within a list data structure, yet it contains an invalid pointer dereference that occurs when processing malformed MP4 files. The flaw arises from insufficient input validation and proper memory management when handling crafted file structures that manipulate list pointers in unexpected ways. When a maliciously constructed MP4 file is processed by MP4Box, the function attempts to dereference a pointer that either points to freed memory or contains invalid memory addresses, leading to a crash of the application.
The operational impact of this vulnerability extends beyond simple application instability, as it can be exploited to create persistent denial of service conditions in systems that rely on GPAC for multimedia processing. Attackers can craft specific MP4 files that trigger the invalid pointer dereference, causing MP4Box to terminate unexpectedly and potentially leading to service disruption in multimedia servers, content delivery networks, or any system that processes MP4 files through GPAC. This vulnerability is particularly dangerous in automated environments where multimedia processing pipelines may be continuously processing files, as it can lead to cascading failures and system unavailability.
From a cybersecurity perspective, this vulnerability maps to CWE-476, which describes NULL pointer dereference conditions that can lead to application crashes and denial of service scenarios. The ATT&CK framework categorizes this as a denial of service technique through application-level exploitation, where adversaries leverage software flaws to make systems unavailable to legitimate users. The vulnerability demonstrates the importance of proper input validation and memory management in multimedia processing libraries, as these components often handle untrusted input from various sources. Organizations using GPAC should prioritize patching to version 0.8.0 or later, as this release includes the necessary fixes to prevent the invalid pointer dereference condition. Additionally, implementing proper file validation and sanitization measures at the system level can provide additional defense-in-depth protection against similar vulnerabilities in multimedia processing workflows.