GPAC MP4Box EUVD-2025-210003

The victim must actively process a crafted AC4 audio file using GPAC MP4Box, confirmed by CVSS UI:R (user interaction required) and AV:L (local attack vector). The file must contain malformed AC4 DSI data targeting the gf_odf_ac4_cfg_dsi_v1 parsing path - specifically, crafted substream group structures or array index values that trigger NULL pointer dereference before the 26.02.0 NULL-guard patches. No privileges are required of the attacker (PR:N), but the attacker must be able to deliver the crafted file to the victim's filesystem or processing queue. Exploitation is limited to denial of service only; no code execution is possible via this vulnerability based on the confirmed impact scope (C:N/I:N/A:H). Automated media pipelines that ingest externally sourced files without human review effectively reduce the UI:R constraint in practice.

The CVSS 5.5 Medium score reflects a constrained threat model: AV:L (local attack vector) and UI:R (user interaction required) mean exploitation is not remotely triggerable against passive targets. The impact is purely availability (A:H), with no confidentiality or integrity consequences. Practically, this limits the attack surface to scenarios where a victim is induced to open a crafted file with MP4Box - typical in media processing workflows, automated transcoding pipelines, or developer/researcher environments. A publicly available PoC lowers the attacker skill bar, raising real-world risk modestly above what the CVSS score alone suggests. The absence of a CISA KEV listing and no EPSS score in the provided data indicate no observed widespread exploitation. For organizations running MP4Box in automated media ingest pipelines where untrusted files are processed without user review, the effective attack vector may be closer to network-sourced than strictly local, warranting elevated priority in those deployments. Overall, this is a moderate-priority issue: impactful in specific pipeline contexts but low-risk in interactive, user-controlled environments.

An attacker crafts a malicious MP4 or AC4 container with deliberately malformed AC4 DSI metadata - such as invalid substream group counts or out-of-bounds sampling frequency indices - and delivers it to a target via email, file share, or a media processing upload endpoint. When the victim or an automated pipeline invokes MP4Box to inspect or transcode the file, the AC4 parser dereferences a NULL pointer while processing the crafted DSI, causing an immediate crash. A public PoC demonstrating this behavior is available at https://github.com/sigdevel/pocs/blob/main/res/gpac/MP4Box/45/README.md.