CVE-2022-22077 - Understanding and Exploiting a Use-After-Free Vulnerability in Snapdragon's Graphics Dispatcher

*Published: June 2024*


The world of mobile security is constantly evolving, and new vulnerabilities are discovered every year. One particularly interesting bug is CVE-2022-22077, a memory corruption vulnerability found in Qualcomm’s Snapdragon Mobile chips. This flaw exists in the graphics handling code, making some Android devices vulnerable to attack. In this post, we'll break down what this CVE means, how it works, and show an example exploit. Everything is explained in simple terms—with code snippets, references, and exclusive insights.

What is CVE-2022-22077?

CVE-2022-22077 is a use-after-free (UAF) bug affecting the graphics dispatcher logic in Snapdragon Mobile. A use-after-free occurs when a program continues to use a block of memory after it has been freed (released). This can lead to unexpected behavior, crashes, or even full control of the device by an attacker.

Summary:  
> _Memory corruption in graphics due to use-after-free in graphics dispatcher logic in Snapdragon Mobile._

How Was It Discovered?

The vulnerability was publicly reported by Qualcomm in their security bulletin (see References below). It affects various Snapdragon chipsets that use the proprietary display and graphics driver. Attackers can exploit this during certain graphics operations, resulting in arbitrary code execution within the kernel or system context.

The Vulnerable Code

At a high level, the bug lies in the dispatcher logic that handles graphic buffer objects (like textures or images). When these buffers are shared between processes or operations, there is a logic bug that causes a pointer to be used even after the memory was already freed.

Here's some pseudo-code to illustrate this pattern

// Simplified vulnerable dispatcher logic
void process_buffer(Buffer *buf) {
    if (buf->in_use) {
        release_buffer(buf);   // Frees the memory and sets buf->ptr = NULL
    }
    // ... Some code that might reschedule this function ...
    render_buffer(buf->ptr);   // Oops! buf->ptr might now be NULL or reused!
}

If an attacker can control the timing and usage of this buffer, they may be able to force the system to render a buffer that has already been freed—possibly replaced with their own controlled data.

UAF Trigger: Specially crafted sequence forces the system to use a freed buffer pointer.

3. Payload Injection: The attacker quickly reallocates that freed memory for malicious code/data.
4. Code Execution: When the dispatcher processes the corrupted buffer, the attacker’s code is executed.

Here’s a conceptual example in C

// Pseudo-code, for education only!
int main() {
    Buffer *buf = allocate_buffer();
    submit_buffer_to_graphics(buf);

    release_buffer(buf); // Frees buf

    // Attacker reuses the buffer's freed memory
    fake_buffer = (Buffer *)malloc(sizeof(Buffer));
    fake_buffer->ptr = (void*)malicious_code;

    // System tries to render the now-freed (and attacker-controlled) buffer
    render_buffer(fake_buffer->ptr);

    // Execution jumps to attacker's code
}

In a real kernel-level or driver exploit, this would be much more complex but follows the same idea: force the system use something that's already freed, then insert your own data/code.

Affected Devices

Hundreds of millions of Android devices from brands using Qualcomm Snapdragon chips could be affected. The actual impact depends on the driver version, Android patch level, and device vendor updates.

References

- Qualcomm Security Bulletin: June 2022
- NIST NVD Entry for CVE-2022-22077
- Android Security Bulletin

Final Thoughts

CVE-2022-22077 is a textbook example of how a small bug in memory handling can lead to serious security risks on millions of phones worldwide. Understanding the underlying mechanisms is the first step not only for defenders, but also for anyone interested in mobile security research.

Stay patched and stay safe!

*This writeup is exclusive to this post. Please use ethically and responsibly. If you find new details or working exploits based on this vulnerability, consider reporting them through proper channels!*

Timeline

Published on: 10/19/2022 11:15:00 UTC
Last modified on: 10/21/2022 20:18:00 UTC