CVE-2025-55661: GPAC MP4Box v2.4 Opus Parser Heap Buffer Overflow

Technical summary

CVE-2025-55661 is a heap buffer overflow (CWE-122) in GPAC's Opus audio stream parsing logic within MP4Box v2.4. The vulnerability exists in memory-unsafe code that processes Opus audio metadata or frames without proper bounds checking. When a maliciously crafted MP4 file with malformed Opus stream data is processed, the parser writes beyond allocated heap memory, corrupting heap structures and triggering an immediate crash. The overflow is limited to denial of service; code execution is not indicated by current analysis.

Business impact

Organizations using GPAC MP4Box v2.4 for batch media processing, transcoding pipelines, or automated content analysis face service disruption if untrusted or user-supplied MP4 files are processed without validation. Media production environments, streaming platforms, and security tools that rely on MP4Box for format inspection are at risk. An attacker could exploit this to interrupt workflows, delay content delivery, or sabotage automated media processing jobs by submitting poisoned files.

Affected systems

GPAC MP4Box v2.4 is confirmed vulnerable. The vulnerability is specific to Opus audio stream parsing; MP4 files containing other audio codecs or video-only content are not affected. Any system running MP4Box v2.4 as a library or standalone tool is in scope if it processes untrusted MP4 files. Earlier or later versions of GPAC require independent verification against vendor advisories.

Exploitability

Exploitability is straightforward for a DoS attack. An attacker requires only the ability to deliver a crafted MP4 file to a target system and trick a user into opening or processing it (via email, file share, web upload, etc.). No special technical skill is required beyond MP4 file manipulation. The CVSS vector (AV:L, UI:R) reflects local access and user interaction as prerequisites. The attack does not require authentication or elevated privileges. Public exploit code has not been confirmed; however, the defect is a standard buffer overflow, making proof-of-concept development straightforward once the flaw is understood.

Remediation

Upgrade GPAC to a patched version released after June 2026 that addresses the Opus parser heap overflow. Verify the specific patch version against the official GPAC project security advisory or release notes. Interim mitigation includes disabling Opus audio processing if possible, implementing file-based input validation (rejecting malformed MP4 headers), and restricting MP4Box processing to trusted sources only. Consider sandboxing MP4Box in isolated environments to limit blast radius of crashes.

Patch guidance

Check the GPAC project's official repository and security advisories for versions newer than v2.4 that include a fix for CVE-2025-55661. Apply the patch as soon as testing confirms compatibility with your media processing pipeline. If you maintain custom builds or forks of GPAC, prioritize merging the upstream fix into your codebase. Test patched versions against your existing MP4 file inventory to confirm no regressions before production deployment.

Detection guidance

Monitor for repeated crashes or unexpected termination of MP4Box processes when processing specific MP4 files, particularly those with Opus audio streams. Log file processing errors and correlate with user submissions or automated file uploads. Network-based detection is limited since this is a local file parsing issue, but you can implement file-format validation on ingress (verify MP4 headers and Opus stream metadata before passing to MP4Box). Automated regression testing with known-bad samples can catch if the vulnerability is present in your build.

Why prioritize this

While the CVSS score of 5.5 (MEDIUM) reflects limited scope (DoS only, no confidentiality or integrity impact), organizations relying on continuous media processing should prioritize this patch. The flaw requires no special privileges or network access, only a user action, making it a practical attack vector in supply-chain or content-upload scenarios. The vulnerability is not yet on the KEV catalog, but widespread GPAC usage in media tools warrants proactive patching. If MP4Box is part of a critical content pipeline, elevate the priority to match operational risk.

Risk score, explained

CVSS 3.1 score of 5.5 (MEDIUM) is driven by high impact (A:H) on availability, but low attack complexity (AC:L) and no privilege requirements (PR:N). The local attack vector (AV:L) and required user interaction (UI:R) prevent a higher score. For environments where service availability is critical or where MP4Box processes untrusted user content at scale, the effective organizational risk may exceed the base CVSS score.

Frequently asked questions