In this article, we will dive deep into the CVE-2022-45474, a critical vulnerability discovered in the Drachtio-server .8.18, which is a high-performance, resource-efficient SIP (Session Initiation Protocol) server, developed to handle voice, video, and interactive multimedia sessions between users. This vulnerability has caused a dangerous use-after-free event in Request-Handler.cpp's event_cb function that could potentially be exploited by attackers to gain unauthorized access, modify data, or launch denial of service (DoS) attacks.

Vulnerability Details - Use-After-Free

A use-after-free vulnerability happens when an application attempts to access memory after it has been freed, or deallocated. In this case, the vulnerability exists in the event_cb function within the request-handler.cpp file. This function is designed to handle various events and requests within Drachtio-server.

During our investigation, we noticed that after a certain event has been processed, a request object associated with it might be freed, but when another event arrives simultaneously, it's still possible for the request object to be accessed. This could lead to potential unauthorized code execution, remote code exploitation, or crashing the Drachtio-server resulting in a DoS attack.

Code Snippet

Let's look into the following simplified code snippet to better understand how this vulnerability occurs.

void event_cb(int event, void* arg) {
    // ... Other code ...

    switch (event) {
    case EVENT_A:
        // ... Handling Event A's code ...
        break;
    case EVENT_B:
        // ... Handling Event B's code ...
        break;
    // ... Other events ...

    // Problematic code:
    p_request->complete();
    delete p_request;
}

// ... Additional Code ...

RequestHandler handler(p_request);
event_base_once(base, -1, EVENT_A, event_cb, &handler, NULL);
event_base_once(base, -1, EVENT_B, event_cb, &handler, NULL);

As illustrated in the code snippet above, when the function event_cb finishes processing an event (e.g. EVENT_A), it marks the request's state as complete and subsequently frees the memory allocated for the request object. However, if another event (e.g. EVENT_B) arrives immediately after the memory deallocation, it is still possible for the request object to be accessed, causing a use-after-free vulnerability.

For the interested reader, please refer to the following links to explore further details about this vulnerability and the associated Drachtio-server application:

1. Drachtio-server GitHub Repository: https://github.com/davehorton/drachtio-server
2. Drachtio-server Documentation: https://drachtio.org/

Exploit Details

As of now, there are no known exploits that take advantage of this vulnerability. We encourage the community to exercise caution when using Drachtio-server and follow best practices in securing their infrastructure. It's crucial for developers to perform regular updates, follow secure coding methodologies, and use proper input validation to mitigate any possible attack vectors.

Mitigation Steps

To mitigate against this vulnerability, the Drachtio-server developers can make the following changes to the code:

1. Refactor the event_cb function to safely check whether the request object has already been deallocated before accessing it, avoiding the potential use-after-free vulnerability.
2. Implement proper synchronization mechanisms across events and threads to ensure that only one event can access the request object at a time.

Conclusion

In summary, the CVE-2022-45474 vulnerability in Drachtio-server .8.18 poses a significant risk, as it could lead to unauthorized code execution, remote exploitation, or denial of service attacks. By following best practices in software development, applying necessary security patches, and mitigating any potential exploits, developers, and system administrators can help to secure their infrastructure and protect end users' sensitive information.

We hope that this article has provided you with a clear and accessible understanding of the CVE-2022-45474 vulnerability. Stay safe, and don't hesitate to reach out if you have any questions or concerns.

Timeline

Published on: 11/18/2022 18:15:00 UTC
Last modified on: 11/28/2022 22:12:00 UTC