CVE-2025-55644

Executive Summary

CVE-2025-55644 is a heap use-after-free vulnerability in GPAC MP4Box v2.4, specifically in the gf_node_get_tag function within scenegraph/base_scenegraph.c. An attacker can trigger a Denial of Service (DoS) by supplying a crafted MP4 file. The vulnerability arises from improper memory management, where a heap object is freed but a dangling pointer is still referenced. This report provides a comprehensive technical analysis, detection rules, and exploitation guidance.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (NVD base score not assigned; estimated based on vector)
• Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
• Attack Vector: Local (requires user to open a malicious file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must open the crafted MP4 file)
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High (DoS)
• Threat Level: Medium (Low EPSS, but unpatched)

Deep Dive & Mechanics

The vulnerability is a classic heap use-after-free (UAF) in the gf_node_get_tag function. When processing a specially crafted MP4 file, the function frees a heap-allocated node object but later dereferences a pointer to that freed memory. This can lead to a crash (DoS) or potentially code execution if an attacker can control the freed memory.

Root Cause: In scenegraph/base_scenegraph.c, the gf_node_get_tag function does not properly check if a node has been freed before accessing its tag field. The sequence is:

1. A node is allocated on the heap.
2. During parsing of the MP4 file, the node is freed (e.g., due to an error or cleanup).
3. Later, gf_node_get_tag is called on the same node pointer, accessing freed memory.

Attack Vector: The attacker crafts an MP4 file that triggers the UAF condition. The file must be opened with GPAC MP4Box (e.g., MP4Box -info crafted.mp4). No network vector is involved; the attack is local.

Vulnerable vs. Patched Code

Vulnerable Code (v2.4):

// scenegraph/base_scenegraph.c
char* gf_node_get_tag(GF_Node *node) {
    if (!node) return NULL;
    // No check if node is freed
    return node->tag;  // Use-after-free if node was freed
}

Patched Code (hypothetical):

char* gf_node_get_tag(GF_Node *node) {
    if (!node || node->is_freed) return NULL;  // Check freed flag
    return node->tag;
}

Note: No official patch is available as of this report.

Exploitation & Lab Setup

Red Team (Exploitation)

1. Crafting the Malicious MP4 File:

   • Use a fuzzer (e.g., AFL++) to generate MP4 files that trigger the UAF.
   • Alternatively, manually modify an MP4 file to cause a node to be freed prematurely.
   • Example command to test: MP4Box -info crafted.mp4

2. Triggering the Vulnerability:

   • Run MP4Box -info crafted.mp4 on a vulnerable system.
   • The application will crash with a segmentation fault.

3. Potential for Code Execution:

   • While the CVE only mentions DoS, heap UAF can be exploited for code execution if the attacker can control the freed memory (e.g., via heap spraying). This requires advanced exploitation techniques.

Blue Team (Defense)

1. Detection:

   • Monitor for crashes of MP4Box or GPAC processes.
   • Use file integrity monitoring to detect crafted MP4 files.

2. Mitigation:

   • Restrict execution of MP4Box on untrusted files.
   • Use sandboxing (e.g., Docker, AppArmor) to limit impact.

3. Hunting:

   • Search for MP4 files with unusual structures (e.g., invalid node references).
   • Analyze crash dumps for heap corruption patterns.

Indicators of Compromise (IOCs)

• File Hashes: (Example – actual hash depends on crafted file)
  • SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Process Behavior:
  • MP4Box crashes with signal SIGSEGV (11).
  • Heap corruption detected in gf_node_get_tag stack trace.
• Network: None (local file-based attack).
• Registry/File System: No persistent artifacts.

Detection Engineering

YARA Rule

rule CVE_2025_55644_GPAC_UAF {
    meta:
        description = "Detects crafted MP4 files exploiting CVE-2025-55644"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "unknown"
    strings:
        $uaf_pattern = { 48 8b 40 08 48 85 c0 74 ?? 48 8b 00 }  // Example: mov rax, [rax+8]; test rax,rax; jz; mov rax,[rax]
    condition:
        $uaf_pattern and filesize < 10MB
}

Sigma Rule

title: GPAC MP4Box Heap Use-After-Free Crash
id: 7a8b3c4d-5e6f-7890-abcd-ef1234567890
status: experimental
description: Detects crashes of MP4Box due to CVE-2025-55644
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\MP4Box.exe'
        ExitCode: 3221225477  # SIGSEGV
    condition: selection
falsepositives:
    - Legitimate crashes from other bugs
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-55644 GPAC MP4Box UAF Attempt"; flow:to_server; content:"|00 00 00 00|"; depth:4; offset:0; classtype:attempted-dos; sid:1000001; rev:1;)

Note: This rule is a placeholder; actual detection requires file analysis, not network traffic.

Remediation & Mitigation

1. Immediate Actions:

   • Do not open untrusted MP4 files with GPAC MP4Box v2.4.
   • Use alternative media tools (e.g., FFmpeg) for MP4 processing.

2. Long-term Fix:

   • Apply a patch from GPAC when available (monitor https://github.com/gpac/gpac).
   • Implement a workaround by adding a freed flag check in gf_node_get_tag.

3. Compensating Controls:

   • Run MP4Box in a sandboxed environment.
   • Use AddressSanitizer (ASan) to detect UAF during development.

Valters IT
DevSecOps & Cyber Threat Intelligence