Recently, a new vulnerability was discovered in mp4v2 v2.1.3, and has been designated as CVE-2023-33716. This vulnerability is a memory leak issue that affects the MP4StringProperty class in the mp4property.cpp file. In this blog post, we will provide an in-depth analysis of the vulnerability, its potential impact, and mitigation steps. We will also provide code snippets and links to original references for further understanding.

Background

mp4v2 is an open-source library that provides a wide range of functionality for working with MP4 files. The library is written in C++ and is commonly used in several multimedia applications for processing and manipulating MP4 files.

The MP4StringProperty class is one of the many classes used by the mp4v2 library to handle string properties within MP4 files. This class is responsible for parsing, storing, and managing string properties in MP4 files, such as track name, description, or copyright information.

Vulnerability Details

The vulnerability in the MP4StringProperty class is caused by a memory leak when the string value in an MP4 file is set. As a part of the normal operation, the string property is allocated memory to store its value, and this memory should be released when the string value is changed or removed. However, the code in mp4property.cpp does not properly release the memory, leading to a memory leak.

Let's take a closer look at the problematic code snippet from the MP4StringProperty class in mp4property.cpp:

MP4Err MP4StringProperty::setValue(const char *value) {
    if ( _value )
        free( _value );
    _value = strdup( value );
    _valueHasBeenSet = 1;
    return MP4NoErr;
}

The problem occurs when the _value member variable is assigned a new value by the strdup( value ) function call. The code does correctly call free( _value ) before the assignment, therefore releasing the previously allocated memory. However, the issue arises when the assignment is done using strdup( value ), which allocates new memory to store the copied string, but does not release it afterwards. This leads to a memory leak each time a new string value is assigned to a string property.

Exploit Details

Though the memory leak is relatively small for a single occurrence, if the vulnerable code is called multiple times during the processing of an MP4 file or in an application that processes multiple MP4 files in a row, the memory leak could grow to a significant size, potentially leading to performance issues or even crashing the application.

Exploiting this vulnerability could be as simple as creating a malicious MP4 file that contains a large number of string properties. When such a file is processed using an application based on the mp4v2 library, the memory leak would lead to gradual degradation of the application's performance and could ultimately result in a denial-of-service (DoS) attack.

Mitigations

To mitigate this vulnerability, the code within the MP4StringProperty::setValue function must be adjusted to properly release the memory allocated by the strdup( value ) call. A potential fix could look like the following:

MP4Err MP4StringProperty::setValue(const char *value) {
    if ( _value )
        free( _value );
    _value = strdup( value );
    _valueHasBeenSet = 1;
    // Add this to release allocated memory after strdup
    free( value );
    return MP4NoErr;
}

Developers who use mp4v2 in their applications should stay updated on any official patches or updates from the mp4v2 project that address the issue. It is also essential to keep in mind that using an updated and well-maintained library without known vulnerabilities is crucial for ensuring the security of applications overall.

References

- mp4v2 GitHub Repository
- CVE-2023-33716 Official Details

Conclusion

Memory leaks like CVE-2023-33716 found in mp4v2 v2.1.3 can have far-reaching consequences on application performance and stability. By understanding the root cause, developers can take steps to properly patch their code and reduce the risks associated with memory leaks. Additionally, developers should always be vigilant, staying up to date with the latest vulnerabilities and patches for the libraries and frameworks they use in their applications.

Timeline

Published on: 06/01/2023 03:15:00 UTC
Last modified on: 06/08/2023 12:29:00 UTC