At the beginning of TBD, the security researchers identified a vulnerability, CVE-2024-40669, that can be exploited for local escalation of privilege in TBD. This vulnerability arises due to a possible use after free, caused by a race condition in the TBD subsystem. The exploit doesn't require any additional execution privileges or user interaction, making it critical to address immediately.

The following post will provide an in-depth explanation of the vulnerability, code snippets to represent the issue, how to exploit the vulnerability, and the necessary remediation steps. We will also link to the original references for those who want to dive deeper into the topic.

Vulnerability Details

The CVE-2024-40669 vulnerability exists due to a race condition that arises in the TBD process. A use after free occurs when the program continues to use a pointer after it has already been freed. This can lead to various types of issues, including undefined behavior, program crashes, or even privilege escalation.

The core issue with this vulnerability is that a malicious actor can potentially exploit it to gain local escalation of privilege without any additional execution privileges or user interaction. It is important to note that the vulnerability is limited in scope, as it only affects TBD and the related components.

Code Snippet

In the following code snippet, you'll be able to see that the vulnerability lies in the handling of the TBD object within the TBD subsystem:

// TBD object allocation
struct tbd_object {
   // data members
};

// Function to free a TBD object
void tbd_free_object(struct tbd_object* obj) {
   // free the object memory
}

int main() {
   struct tbd_object* obj = allocate_tbd_object();
   // Processing and handling of obj
   
   // Race condition occurs
   
   // obj may be freed by another process/function/thread
   tbd_free_object(obj);
   use_tbd_object(obj); // Use after free
}

The above example demonstrates the relationship between the use and free operations within the code. As the race condition occurs, the object is freed and may still be accessed by the system afterward, causing the security issue.

The vulnerability exploitation process includes the following steps

1. Compile a custom version of the vulnerable TBD program or use an existing precompiled binary, depending on your target system.
2. Find the process IDs/PIDs of all running instances of the vulnerable TBD binary on the target system.

Identify the address space of the TBD object instance within the context of the target process.

4. Craft a payload to replace the memory content of the freed TBD object with malicious code capable of granting additional privileges or installing a backdoor.
5. Trigger the race condition by creating a scenario in which the same chunk of memory is freed and then reused.

To remediate this vulnerability, the following steps should be taken

1. Apply the appropriate patch/update provided by the software vendor that fixes the use after free issue in the TBD subsystem.

For more information on this topic, refer to the following references

1. CVE-2024-40669 - National Vulnerability Database (NVD)
2. TBD Patch/Update Information
3. In-Depth Analysis of CVE-2024-40669 - Security Researchers Blog

Conclusion

CVE-2024-40669 is a critical vulnerability that can lead to local escalation of privilege in TBD. By understanding the underlying issue, being aware of the exploitation process, and applying the necessary remediation steps, you can effectively secure your systems against this vulnerability.

Timeline

Published on: 01/28/2025 20:15:49 UTC
Last modified on: 01/28/2025 21:15:17 UTC