CVE-2025-25942

Executive Summary

CVE-2025-25942 is a memory leak vulnerability in Bento4 v1.6.0-641, specifically within the mp4fragment tool. The issue resides in the SampleArray::SampleArray constructor in Mp4Fragment.cpp, where allocated memory is not properly released when processing malformed or invalid MP4 files. This can lead to resource exhaustion (denial of service) and potentially information disclosure through residual memory contents. The vulnerability has a CVSS score of 0.0 (unscored) and no public exploit or patch is currently available. The EPSS score is 0.0%, indicating low exploitation activity in the wild.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unscored)
• Attack Vector (AV): Local (L) – requires processing a crafted file
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): Required (R) – user must open the file with mp4fragment
• Scope (S): Unchanged (U)
• Confidentiality (C): Low (L) – potential information leak
• Integrity (I): None (N)
• Availability (A): Low (L) – memory exhaustion

Threat Level: Medium (due to potential information disclosure and DoS)

Deep Dive & Mechanics

The vulnerability is a classic memory leak in C++ code. The SampleArray class in Mp4Fragment.cpp allocates memory for sample data during construction. When the mp4fragment tool processes a malformed MP4 file, the parsing logic may encounter errors before the allocated memory is freed. The destructor of SampleArray is not called, or the cleanup code is bypassed, leaving allocated memory unreachable.

Root Cause: The SampleArray::SampleArray constructor allocates memory (e.g., via new or malloc) but the corresponding delete or free is not guaranteed to be called in all error paths. This is a CWE-401: Missing Release of Memory after Effective Lifetime.

Impact:

• Denial of Service: Repeatedly processing crafted files can exhaust system memory.
• Information Disclosure: Unfreed memory may contain sensitive data from previous allocations (e.g., other file contents, encryption keys). An attacker could craft a file that triggers the leak and then read the leaked memory via a side channel or by analyzing the tool's output.

Vulnerable vs. Patched Code

Vulnerable Code (Bento4 v1.6.0-641):

// Mp4Fragment.cpp (simplified)
class SampleArray {
public:
    SampleArray() {
        data = new uint8_t[INITIAL_SIZE]; // allocation
    }
    // No destructor or cleanup in error paths
};

void processFile() {
    SampleArray samples;
    // ... parsing logic that may throw or return early
    // samples destructor not called if exception thrown
}

Patched Code (Hypothetical):

class SampleArray {
public:
    SampleArray() : data(nullptr) {}
    ~SampleArray() {
        delete[] data; // proper cleanup
    }
    // Use RAII or smart pointers
};

void processFile() {
    std::unique_ptr<SampleArray> samples = std::make_unique<SampleArray>();
    // ... parsing with proper exception handling
}

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install Bento4 v1.6.0-641 on a Linux VM.
2. Create a malformed MP4 file that triggers the memory leak (e.g., corrupt the stsz atom or provide an invalid sample count).
3. Run mp4fragment on the crafted file repeatedly.

Exploitation Steps:

• Use a fuzzer (e.g., AFL++) to generate inputs that maximize memory allocation without freeing.
• Monitor memory usage with top or /proc/meminfo.
• To exploit information disclosure, craft a file that causes the leak to retain sensitive data from previous allocations (e.g., by first loading a file with known secrets, then triggering the leak).

No public exploit code is available.

Blue Team

Detection:

• Monitor for excessive memory usage by mp4fragment processes.
• Use strace or ltrace to detect abnormal allocation patterns.
• Implement file integrity monitoring for Bento4 binaries.

Hunting:

• Search for logs indicating crashes or out-of-memory conditions.
• Analyze network traffic for bulk transfer of MP4 files to/from Bento4 servers.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available – generate upon discovery)
• Process Names: mp4fragment
• Memory Patterns: Unusually high memory consumption by mp4fragment (e.g., >1GB for small input files)
• Network: No specific network IOCs (local vulnerability)
• Registry/File System: Modified Bento4 binaries or libraries

Detection Engineering

YARA Rule

rule CVE_2025_25942_Bento4_MemoryLeak {
    meta:
        description = "Detects Bento4 mp4fragment binary with vulnerable SampleArray allocation"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-25942"
    strings:
        $s1 = "SampleArray" ascii wide
        $s2 = "Mp4Fragment.cpp" ascii wide
        $s3 = "new uint8_t" ascii wide
    condition:
        all of them
}

Sigma Rule

title: Bento4 mp4fragment Memory Leak Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects excessive memory usage by mp4fragment indicating CVE-2025-25942 exploitation
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/mp4fragment'
        CommandLine|contains: '*.mp4'
    condition: selection
    timeframe: 5m
    aggregation:
        field: Image
        function: sum(WorkingSetSize)
        condition: gt 1073741824  # >1GB
falsepositives:
    - Legitimate processing of very large MP4 files
level: medium

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-25942 Bento4 mp4fragment Memory Leak - Potential DoS"; flow:to_server; content:"|00 00 00 00|"; depth:4; byte_test:4,>,1000000,0,relative; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Do not use Bento4 v1.6.0-641 for processing untrusted MP4 files.
2. Isolate the mp4fragment tool in a sandboxed environment (e.g., Docker with memory limits).
3. Monitor memory usage of Bento4 processes.

Long-term Fix:

• Apply proper memory management using RAII (e.g., std::vector or std::unique_ptr).
• Add exception-safe cleanup in all error paths.
• Update to a patched version when available.

Workarounds:

• Use alternative MP4 fragmentation tools (e.g., FFmpeg, GPAC).
• Pre-validate MP4 files with a separate tool before processing.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert