CVE-2019-20630 in GPAC
Summary
by MITRE
An issue was discovered in libgpac.a in GPAC before 0.8.0, as demonstrated by MP4Box. It contains a heap-based buffer over-read in BS_ReadByte (called from gf_bs_read_bit) in utils/bitstream.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-2019-20630 represents a critical heap-based buffer over-read flaw within the GPAC multimedia framework library. This issue specifically affects versions prior to 0.8.0 and manifests in the libgpac.a component when processing MP4 files through the MP4Box utility. The vulnerability arises from improper bounds checking during bitstream parsing operations, creating a scenario where maliciously crafted MP4 files can trigger memory access violations. The flaw is particularly concerning as it can be exploited to cause denial of service conditions, effectively rendering the affected system or application unavailable to legitimate users. The vulnerability stems from the BS_ReadByte function within the utils/bitstream.c file, which is invoked by gf_bs_read_bit during the parsing of multimedia content.
The technical implementation of this vulnerability involves a classic buffer over-read condition where the application attempts to read memory beyond the allocated buffer boundaries. When MP4Box processes a specially crafted file, the bitstream parsing logic fails to properly validate the size of data being read, causing the BS_ReadByte function to access memory locations that do not belong to the intended buffer. This over-read condition can lead to unpredictable behavior including application crashes, memory corruption, or system instability. The vulnerability operates at the bitstream parsing layer, making it particularly dangerous as it can be triggered during normal file processing operations without requiring special privileges or user interaction. The flaw demonstrates poor input validation practices and highlights the importance of robust bounds checking in multimedia processing libraries that handle untrusted input data.
The operational impact of CVE-2019-20630 extends beyond simple denial of service to potentially compromise system stability and availability. Attackers can exploit this vulnerability by crafting malicious MP4 files that, when processed by any application utilizing the vulnerable GPAC library, will trigger the buffer over-read condition. This creates a significant risk for multimedia applications, content delivery networks, and systems that process user-uploaded media files. The vulnerability affects a wide range of applications that depend on GPAC for multimedia processing, including video players, content management systems, and streaming platforms. The exploitability of this issue is relatively straightforward, requiring only the creation of a malformed MP4 file rather than complex attack vectors. Organizations using GPAC-based applications are particularly vulnerable as this flaw can be leveraged to disrupt services or cause system crashes across multiple platforms where GPAC is integrated.
Mitigation strategies for CVE-2019-20630 primarily focus on immediate version updates to GPAC 0.8.0 or later, which contain the necessary patches to address the buffer over-read condition. System administrators should prioritize updating all applications and services that rely on the affected GPAC library to prevent exploitation. Additionally, implementing input validation measures such as file format verification and size restrictions can provide additional defense-in-depth layers. Network administrators should consider deploying intrusion detection systems that can identify and block suspicious MP4 file patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and demonstrates characteristics consistent with attack techniques found in the ATT&CK framework under the T1203 category for exploitation of remote services. Organizations should also implement monitoring protocols to detect unusual application behavior that may indicate exploitation attempts, particularly in environments where multimedia file processing is common. Regular security assessments and vulnerability scanning should be conducted to ensure all systems utilizing GPAC components remain protected against similar issues.