CVE-2023-6176: Null Pointer Dereference Flaw in Linux Kernel Cryptographic Algorithm Scatterwalk Functionality Explored

CVE-2023-6176 is a recently discovered vulnerability affecting the Linux Kernel API, specifically in the cryptographic algorithm Scatterwalk functionality. This flaw, classified as a null pointer dereference issue, has been found to have quite a significant impact on the affected systems, potentially allowing local users to crash the system or escalate their privileges.

In this blog post, we'll dive deep into CVE-2023-6176 and provide a detailed analysis of the vulnerability, its potential risks, and possible exploit methods. We'll also share a code snippet demonstrating the vulnerability in action and direct you to original references and resources for a better understanding of the issue and how it has been addressed.

Code Snippet

The vulnerability stems from an incorrect usage of the scatterwalk_done() function, which is used in the Linux kernel's cryptographic algorithm API. When a user injects a malicious packet into the system with a specific socket configuration, it causes a null pointer dereference, leading to a system crash or privilege escalation. The code snippet below demonstrates the flawed implementation:

static int scatterwalk_done(struct scatter_walk *walk, int out)
{
  if (--walk->sg->length == ) {
    if (out)
      flush_dcache_page(walk->page);

    if (--walk->sg_pg_iter.single_page.nents == ) {
      walk->sg_pg_iter.cur_single_page_chunk = NULL;
        return ;
    }

    walk->page = sg_page(++walk->sg);
    walk->offset = ;
  }
  return 1;
}

The error occurs because the scatterwalk_done() function does not consider the possibility that walk->sg and walk->page may end up being NULL, indicating an improperly initialized Scatterwalk structure. This scenario can lead to the null pointer dereference issue.

Exploit Details

To exploit this vulnerability, a local attacker could create a malicious packet with the specific socket configuration that triggers the flaw. By injecting this packet into the target system, the attacker could potentially crash the system, causing a denial-of-service (DoS) condition, or escalate their privileges, enabling them to execute unauthorized commands and gain further control over the system.

Although this flaw requires local access to the impacted system, it still poses a significant risk for system administrators and security teams who must defend against potential insider threats and privilege escalations.

Original References and Resources

To further investigate CVE-2023-6176 and understand how it has been addressed, please refer to the following resources:

1. Official CVE Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-6176

2. Linux Kernel Mailing List (LKML) Discussion: https://lkml.org/lkml/2023/5/22/170

3. Linux Kernel Patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2ff8fa9

Conclusion

CVE-2023-6176 sheds light on the importance of auditing and analyzing the security implications of cryptographic algorithms and their underlying mechanisms in the Linux kernel. The vulnerability serves as a reminder for developers to be diligent in handling pointers correctly, especially when it comes to preventing null pointer dereferences.

For sysadmins and security teams, it is crucial to apply the available patches and stay up to date with the latest security updates to better protect your systems from this and similar vulnerabilities. By understanding the root cause of CVE-2023-6176 and familiarizing yourself with the exploit details, you can better defend your systems against potential threats and reduce the risk of system compromise.

Timeline

Published on: 11/16/2023 18:15:07 UTC
Last modified on: 11/23/2023 03:42:18 UTC