CVE-2024-31002

Executive Summary

CVE-2024-31002 is a critical buffer overflow vulnerability discovered in Bento4, version 1.6.0-641. The flaw resides in the AP4_BitReader::ReadCache() function within the Ap4Utils.cpp component. A remote attacker can exploit this vulnerability by crafting a malicious input that triggers a buffer overflow, potentially leading to arbitrary code execution on the target system. The vulnerability has a CVSS score of 0.0, indicating that it has not been officially scored, but the nature of the flaw suggests a high severity. No public proof-of-concept (PoC) or patch details are currently available, making this a high-risk, unpatched vulnerability.

Supply Chain & Package Security

Bento4 is a C++ library for MP4 file parsing and manipulation, commonly used in media processing applications. As a library, it is often integrated into larger projects via source code or package managers. The lack of a patch and the potential for remote code execution make this a significant supply chain risk. Any application that uses the vulnerable version of Bento4 to parse untrusted MP4 files is at risk. Organizations should audit their dependencies for Bento4 version 1.6.0-641 and consider isolating or sandboxing media processing tasks until a patch is available.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which typically indicates that the score has not been calculated or is pending. However, based on the vulnerability description (buffer overflow leading to arbitrary code execution), the likely CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The exploit affects only the vulnerable component.
• Confidentiality (C): High (H) – Arbitrary code execution can lead to data exfiltration.
• Integrity (I): High (H) – Code execution allows modification of data.
• Availability (A): High (H) – Code execution can disrupt service.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Estimated Score: 9.8 (Critical)

Threat Level: Critical. The vulnerability is remotely exploitable, requires no authentication, and can lead to full system compromise.

Deep Dive & Mechanics

The vulnerability is a classic buffer overflow in the AP4_BitReader::ReadCache() function. This function is responsible for reading bits from a cache buffer. The flaw occurs when the function attempts to read more bits than are available in the cache, leading to an out-of-bounds read or write.

Root Cause:
The ReadCache() function likely lacks proper bounds checking. When the number of bits requested exceeds the remaining bits in the cache, the function may read beyond the allocated buffer, corrupting adjacent memory.

Attack Vector:
An attacker can craft a malicious MP4 file (or other media format parsed by Bento4) that contains specially crafted bitstream data. When Bento4 processes this file, the ReadCache() function is called with a large bit count, triggering the overflow.

Impact:
Successful exploitation can allow an attacker to overwrite critical data structures, such as function pointers or return addresses, leading to arbitrary code execution. This could be used to install malware, exfiltrate data, or pivot to other systems.

Vulnerable vs. Patched Code

Since no patch is available, we can only analyze the vulnerable code pattern. The vulnerable function likely looks like this:

// Vulnerable code (hypothetical)
void AP4_BitReader::ReadCache(unsigned int bits) {
    while (bits > m_CacheBits) {
        // Read more data from stream into cache
        unsigned char byte = ReadByte();
        m_Cache = (m_Cache << 8) | byte;
        m_CacheBits += 8;
    }
    // No check if m_CacheBits is sufficient
    m_CacheBits -= bits;
    // Return bits from cache
}

A patched version would include a bounds check:

// Patched code (hypothetical)
void AP4_BitReader::ReadCache(unsigned int bits) {
    if (bits > m_CacheBits + (m_StreamSize - m_StreamPos) * 8) {
        // Handle error: not enough bits available
        throw std::runtime_error("Buffer overflow attempt");
    }
    while (bits > m_CacheBits) {
        unsigned char byte = ReadByte();
        m_Cache = (m_Cache << 8) | byte;
        m_CacheBits += 8;
    }
    m_CacheBits -= bits;
}

The key difference is the addition of a check to ensure that the requested number of bits does not exceed the total available bits in the stream.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Bento4 version 1.6.0-641 installed on a target system.
• Ability to deliver a malicious MP4 file to the target (e.g., via email, web download, or network share).

Exploitation Steps:

1. Craft Malicious Input: Create a specially crafted MP4 file that triggers the overflow. This requires reverse engineering the ReadCache() function to determine the exact bit offset and payload placement.
2. Deliver Payload: Send the malicious file to the target. This could be done via phishing, a compromised website, or direct file transfer.
3. Trigger Vulnerability: When the target application (e.g., a media player or converter) uses Bento4 to parse the file, the overflow occurs.
4. Achieve Code Execution: Overwrite a return address or function pointer to redirect execution to shellcode embedded in the file.

Example (Conceptual):

# Python script to generate a malicious MP4 file (conceptual)
import struct

def create_malicious_mp4():
    # Craft a malformed MP4 atom that triggers the overflow
    # This is a simplified example; actual exploitation requires detailed analysis
    payload = b"A" * 1000  # Overflow data
    # ... build MP4 structure with malformed bitstream
    with open("exploit.mp4", "wb") as f:
        f.write(payload)

create_malicious_mp4()

Note: No public exploit code is available. The above is a conceptual example.

Blue Team (Defensive)

Detection:

• Monitor for unusual MP4 files being processed by applications using Bento4.
• Use network monitoring to detect large or malformed MP4 files being transferred.
• Implement file integrity monitoring on critical systems.

Mitigation:

• Isolate media processing in a sandboxed environment.
• Use input validation to reject malformed MP4 files before they reach Bento4.
• Apply strict memory protections (ASLR, DEP, CFG) to mitigate exploitation.

Indicators of Compromise (IOCs)

• File Hashes: (No specific hashes available; monitor for files with unusual sizes or structures)
• Network Indicators: Unusual MP4 file transfers to/from internal systems.
• Process Behavior: Bento4 processes crashing or exhibiting abnormal memory access patterns.
• Registry/File System: Unexpected files created in temporary directories by media processing applications.

Detection Engineering

YARA Rule

rule CVE_2024_31002_Bento4_Overflow {
    meta:
        description = "Detects malicious MP4 files targeting CVE-2024-31002"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-31002"
    strings:
        $bento4_magic = { 00 00 00 18 66 74 79 70 }  // ftyp atom
        $overflow_pattern = { FF FF FF FF }  // Potential overflow trigger
    condition:
        $bento4_magic at 0 and #overflow_pattern > 5
}

Sigma Rule

title: CVE-2024-31002 Bento4 Buffer Overflow Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit CVE-2024-31002 via malformed MP4 files
author: Valters IT
logsource:
    category: file_event
    product: windows
detection:
    selection:
        EventID: 11  # FileCreate
        TargetFilename|endswith: '.mp4'
        TargetFilename|contains: 'exploit'
    condition: selection
falsepositives:
    - Legitimate MP4 files with unusual names
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET any (msg:"CVE-2024-31002 Bento4 MP4 Overflow Attempt"; flow:to_client; content:"|00 00 00 18 66 74 79 70|"; depth:8; content:"|FF FF FF FF|"; distance:0; within:1000; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate: Discontinue use of Bento4 version 1.6.0-641 in production environments until a patch is available.
2. Monitor: Implement the detection rules above to identify potential exploitation attempts.
3. Sandbox: Run any application that uses Bento4 in a sandboxed or containerized environment with limited privileges.

Long-term Fix:

• Apply a patch from the vendor once released. Monitor the Bento4 GitHub repository for updates.
• Consider switching to an alternative MP4 parsing library that is actively maintained and patched.

Workarounds:

• Implement input validation to reject MP4 files with unusual bitstream structures.
• Use a Web Application Firewall (WAF) or network filter to block known malicious patterns.

Valters IT
Securing Digital Frontiers