CVE-2024-9632: Uncovering the Buffer Overflow Flaw in X.org Server

In today's digital world, it's not uncommon to hear about vulnerabilities being discovered and exploited in various software applications. One such vulnerability, identified as CVE-2024-9632, has been found in the X.org server, which is a widely-used open-source implementation of the X Window System for UNIX and Linux platforms. This vulnerability presents a potential risk for exploitation, leading to denial of service (DoS) attacks or local privilege escalation in distributions where the X.org server is run with root privileges. In this blog post, we will delve into the details of this vulnerability, explore the code snippets involved, and discuss exploit details.

Background on the vulnerability

The issue at hand is found in the _XkbSetCompatMap function of X.org, where an improper tracking of allocation size can lead to a buffer overflow condition. Specifically, a local attacker can trigger this condition by crafting a special payload, ultimately causing a denial-of-service attack or, in some instances, local privilege escalation.

Code Snippet

void _XkbSetCompatMap(...)
{
    ...
    xkbClientMapPtr map = dpy->xkb_info->client;
    int num_si = map->compat->max_si;
    // Allocation size for 'tmp_si' is determined by 'num_si' only
    // which can be controlled by user.
    XkbSIRec *tmp_si = _XkbTypedCalloc(num_si, XkbSIRec);
    ...
    // Exploit: Trigger Buffer Overflow condition.
    for (i = ; i < num_si; i++) {
        ...
        // The following memcpy can result in a buffer overflow:
        memcpy(&tmp_si[i], &map->compat->syms[ptr[i]], size_of_XkbSIRec);
    }
    ...
}

As seen in the code snippet above, the allocation size for 'tmp_si' is determined by 'num_si,' a variable that can be controlled by the user. Later in the code, a memcpy operation is performed, which can lead to a buffer overflow condition. This is the crux of the problem and the gateway for an attacker to exploit the vulnerability.

For more information about this vulnerability, you can review the following original references

1. CVE-2024-9632 Details
2. X.org Server Official Website
3. X Window System Explained

Exploit Details

Given that the vulnerability lies within a buffer overflow condition, an attacker can exploit it using the following methods:

1. Craft a specifically designed payload that would trigger the buffer overflow condition, leading to denial of service or privilege escalation.

2. Deploy social engineering tactics to convince the victim to run arbitrary code, causing the buffer overflow condition and consequent attack.

Remember that this vulnerability affects systems where the X.org server runs with root privileges. In such cases, a successful attack can result in significant damage to the system, further highlighting the necessity of addressing this vulnerability.

Conclusion

As the world continues to rely more and more on digital systems, it becomes imperative to stay vigilant and informed about the vulnerabilities that may affect the software we use daily. CVE-2024-9632 serves as an example of how a seemingly small flaw in X.org's server implementation can lead to potentially significant consequences. By staying educated and up-to-date with such vulnerabilities, we can better protect our systems and minimize risks.

Timeline

Published on: 10/30/2024 08:15:04 UTC
Last modified on: 12/26/2024 14:22:23 UTC