CVE-2025-55643 Overview
CVE-2025-55643 is a NULL pointer dereference vulnerability in the TrackWriter handling component of GPAC MP4Box version 2.4. The flaw resides in filters/mux_isom.c and is triggered when the application processes a crafted MP4 file. Attackers can exploit this issue to cause a Denial of Service (DoS) condition, terminating the MP4Box process. The vulnerability requires local access and user interaction, since a victim must open or process the malicious media file. The weakness is classified under [CWE-476] (NULL Pointer Dereference).
Critical Impact
Processing a crafted MP4 file with GPAC MP4Box v2.4 causes a NULL pointer dereference in the TrackWriter component, resulting in a Denial of Service against the application.
Affected Products
- GPAC MP4Box version 2.4
- GPAC multimedia framework (filters/mux_isom.c component)
- Applications and workflows that embed GPAC for MP4 muxing
Discovery Timeline
- 2026-06-15 - CVE-2025-55643 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-55643
Vulnerability Analysis
The vulnerability resides in the TrackWriter handling logic implemented within filters/mux_isom.c in GPAC MP4Box v2.4. GPAC is an open-source multimedia framework used for packaging, streaming, and playback of audio and video content. MP4Box, one of its primary command-line tools, parses and muxes ISO Base Media File Format (ISOBMFF) containers such as MP4.
When MP4Box processes a specially crafted MP4 file, the TrackWriter component dereferences a pointer that was never initialized or has been freed. The unchecked pointer access causes the process to crash, terminating any in-progress muxing or transcoding operation. The flaw does not enable code execution or data disclosure based on available references.
Root Cause
The root cause is a missing NULL check on a pointer used by the TrackWriter routine in filters/mux_isom.c. The parser accepts malformed track metadata in the input MP4 without validating that required structures were successfully allocated or populated. Subsequent code paths dereference the resulting NULL pointer, producing a segmentation fault.
Attack Vector
Exploitation requires local access and user interaction. An attacker delivers a crafted MP4 file to a user or automated pipeline that processes media with GPAC MP4Box. When MP4Box opens the file, the TrackWriter logic dereferences the NULL pointer and the process terminates. Impact is limited to availability of the MP4Box process and any dependent workflow.
No verified proof-of-concept code is publicly indexed. For technical context, see the OpenWall OSS Security Update and the InfoSec Exchange Post.
Detection Methods for CVE-2025-55643
Indicators of Compromise
- Unexpected crashes or segmentation faults of the MP4Box process during MP4 ingestion or muxing.
- Core dumps referencing mux_isom.c or the TrackWriter routine on the call stack.
- Repeated processing failures tied to specific user-supplied MP4 files in media pipelines.
Detection Strategies
- Monitor application logs from media processing services for abnormal MP4Box termination codes.
- Inspect submitted MP4 files with MP4Box -info in a sandboxed environment before production processing.
- Correlate process termination events with the hashes of recently ingested media files to identify a malicious source.
Monitoring Recommendations
- Enable core dump capture on hosts running GPAC to support post-crash triage.
- Alert on repeated non-zero exits of MP4Box within media transcoding queues.
- Track GPAC version inventory across servers and developer workstations to confirm exposure to v2.4.
How to Mitigate CVE-2025-55643
Immediate Actions Required
- Identify all hosts running GPAC MP4Box v2.4 and restrict their ability to process untrusted MP4 files.
- Route untrusted media through an isolated sandbox or container with strict resource limits and no production data access.
- Validate and reject MP4 files from untrusted origins at the ingestion boundary until a fixed build is deployed.
Patch Information
No official fixed version is referenced in the available advisories at the time of publication. Track the GPAC project repository and the OpenWall OSS Security Update for an upstream patch addressing the TrackWriter NULL pointer dereference in filters/mux_isom.c. Rebuild from source once a fix is merged, or upgrade to a vendor-provided release containing the corrected code.
Workarounds
- Disable or remove MP4Box from systems that do not require ISOBMFF muxing functionality.
- Run MP4Box under a low-privilege service account with automatic restart, limiting impact of a crash to the affected job.
- Apply file-type and structural validation on incoming MP4 files using an alternate parser before handing them to GPAC.
- Implement watchdog logic that detects and contains repeated MP4Box crashes from the same source file.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
