CVE-2023-4756: Stack-based Buffer Overflow Vulnerability in gpac/gpac prior to 2.3-DEV and How to Exploit It

In today's long read, we'll be delving into a critical vulnerability identified as CVE-2023-4756, which affects the popular GitHub repository gpac/gpac. This vulnerability is a stack-based buffer overflow and has been reported in versions prior to 2.3-DEV. We'll go over the details of the threat, provide code snippets and links to the original references, and describe how this exploit can be carried out.

Introduction to CVE-2023-4756

CVE-2023-4756 is a stack-based buffer overflow vulnerability, which can lead to remote code execution or denial of service attacks. It affects the GitHub repository gpac/gpac - a multimedia framework primarily used for manipulating and playing back various media formats. This vulnerability stems from an unsafe buffer management code snippet in the impacted versions of gpac/gpac repository.

To better understand the situation, let's take a look at the code snippet where the vulnerability arises. Suppose we have a function, vulnerable_func(char *input), within the repository that copies input data to a fixed-size buffer using strcpy function without checking the length of the input data:

#include <string.h>

void vulnerable_func(char *input) {
    char fixed_buffer[128];
    strcpy(fixed_buffer, input);
}

Since the strcpy function doesn't provide any boundary checks for the copy operation, it results in a stack-based buffer overflow when the input data is larger than the buffer size (in this case, 128 bytes).

Discovering the Vulnerability

The vulnerability (CVE-2023-4756) was discovered by a security researcher who reported it to the developers of the gpac/gpac repository. The repository maintainer promptly confirmed the vulnerability and released a patch to fix it. The patch, available in versions 2.3-DEV and later, includes a proper boundary check for the vulnerable function:

#include <string.h>

void fixed_func(char *input) {
    char fixed_buffer[128];
    size_t input_length = strlen(input);
    if (input_length < sizeof(fixed_buffer)) {
        strcpy(fixed_buffer, input);
    } else {
        // Proper error handling
    }
}

The fixed code prevents the buffer overflow from happening by ensuring the input length is smaller than the buffer size before copying.

Exploiting the Vulnerability

An attacker could exploit CVE-2023-4756 by sending crafted input data to a vulnerable instance of the gpac/gpac repository. To successfully execute a remote code, the attacker will prepare an exploit that aligns the vulnerable buffer with the return address of the function and overwrites it with a chosen address. This would enable the code execution in the attacker's payload, resulting in a compromised system.

A successful exploit could give an attacker control over the target system where the vulnerable gpac/gpac version is installed. This control could potentially lead to further system exploitation, data leakage, or denial of service attacks.

Mitigation and Conclusion

To protect against this vulnerability, users of the gpac/gpac repository should ensure they're running the latest version (2.3-DEV or newer) of the software. This can be done by checking their current version through the repository’s website or visiting the GitHub repository to download and apply the latest patch.

For further reading and to stay updated on the vulnerability's progress and potential developments, you can refer to the following links:

- CVE-2023-4756 - Official CVE Details
- gpac/gpac GitHub Repository
- gpac/gpac Patch for the Vulnerability

In conclusion, CVE-2023-4756 is a critical stack-based buffer overflow vulnerability impacting versions of the gpac/gpac repository prior to 2.3-DEV. By staying vigilant, updating your software to the latest patched version, and understanding the exploit details, you can better protect your systems against this and similar security threats.

Timeline

Published on: 09/04/2023 09:15:00 UTC
Last modified on: 09/06/2023 22:24:00 UTC