CVE-2023-4755 - Use After Free Vulnerability Found in gpac/gpac Prior to 2.3-DEV: Exploit Details, Code Snippet, and Important Links

A newly identified vulnerability, CVE-2023-4755, has been found in the GitHub repository gpac/gpac versions before 2.3-DEV. This vulnerability is a use-after-free issue, which means that the application may unintentionally use memory after it has been freed, leading to potential corruption of data, denial of service, or even execution of arbitrary code. In this post, we'll dive into the details of this vulnerability, show an example of the triggering code snippet, and provide relevant links for further reading and references.

Exploit Details

The CVE-2023-4755 vulnerability is present in the gpac multimedia framework (https://github.com/gpac/gpac), specifically in versions prior to 2.3-DEV. This framework is widely used for processing multimedia content, and the vulnerability may allow an attacker to exploit the software through a specially crafted media file.

The issue resides in the ISOBMFF box parsing, which incorrectly handles memory allocation and deallocation in certain situations. As a consequence, the application may attempt to access and use a portion of memory that has already been freed, leading to undefined behavior and potential exploitation opportunities for an attacker.

Code Snippet

To demonstrate the vulnerability, let's analyze the following code snippet from the file "box_code_base.c":

void gf_isom_box_array_del(GF_List *list) {
  u32 count, i;
  GF_Box *a;
  if (!list) return;
  count = gf_list_count(list);
  for (i = ; i < count; i++) {
    a = (GF_Box *)gf_list_get(list, i);
    if (a) {
      gf_isom_box_del(a);      
      /* Memory is freed here, but still present in the list */
    }
  }
  gf_list_del(list);
}

The function gf_isom_box_array_del() iterates through a list of boxes to delete each of them. However, after calling gf_isom_box_del(a) to free the memory of the box a, the application does not remove the reference to the freed box in the list. This can lead to an accidental use of the freed memory later in the application's execution, thus triggering the use-after-free vulnerability.

To learn more about this vulnerability, consult the following references

1. The National Vulnerability Database (NVD) entry for CVE-2023-4755: https://nvd.nist.gov/vuln/detail/CVE-2023-4755
2. The GitHub Security Advisory: https://github.com/gpac/gpac/security/advisories/GHSA-vgq9-q3hq-p698
3. The official gpac GitHub repository: https://github.com/gpac/gpac

Mitigation and Patch

The vulnerability has been patched in version 2.3-DEV of gpac. Upgrading to this version or a later one will fix the issue. To apply the upgrade, follow the instructions provided in the project's GitHub repository: https://github.com/gpac/gpac

Conclusion

The CVE-2023-4755 use-after-free vulnerability in the gpac multimedia framework highlights the importance of proper memory management in applications, especially those responsible for processing user-generated content. Users of the affected software should upgrade to version 2.3-DEV or a later one to mitigate the risk of exploitation. Stay informed about similar security issues by keeping an eye on official advisory channels, such as NVD and GitHub Security Advisories.

Timeline

Published on: 09/04/2023 14:15:00 UTC
Last modified on: 09/06/2023 20:43:00 UTC