Android phones run on a complex piece of software called the Linux kernel, which handles everything from memory management to hardware access. In 2022, a serious vulnerability was found in certain Android kernels: CVE-2022-20120. In this deep dive, we’ll break down what happened, how attackers could use this bug, show an overview of potential exploit code, and explain how to keep yourself safe.

What Is CVE-2022-20120?

CVE-2022-20120 is a security vulnerability impacting certain Android kernel versions. The core issue relates to how the kernel processes certain memory operations, which—if triggered by a malicious app or user—can lead to unauthorized access and potentially escalate privileges (i.e., gaining "root" access without permission).

Basic Info

- CVE: CVE-2022-20120

How Does The Vulnerability Work?

The vulnerability is found in Android's customized Linux kernel code. Certain kernel functions didn’t properly validate memory addresses provided by user apps, allowing specially crafted apps to trick the kernel into reading or writing outside of protected memory regions.

Exploit Walkthrough (Simplified)

While detailed actual exploit code is not publicly distributed (and shouldn’t be used maliciously), understanding roughly *how* attackers approach this class of vulnerabilities is important.

Find a Path to the Kernel Function:

The attacker needs to reach a "vulnerable" kernel API, often through ioctl or a device file (for example, /dev/binder, /dev/ashmem, etc).

Trigger Invalid Memory Access:

Carefully craft data that—when passed from user space to kernel space—causes the kernel to read memory outside of the intended buffer. This can expose sensitive data, or, in advanced cases, let an attacker overwrite privileged code.

Achieve Privilege Escalation:

If the attacker can write to kernel memory, they might modify their process credentials to become root.

Basic (Hypothetical) Exploit Snippet

Here’s a simplified C snippet that *conceptually* shows how some Android kernel exploits interact with vulnerable device nodes. (This is not a usable exploit, but for educational purposes).

#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <unistd.h>

#define VULN_IOCTL_CMD x12345678

int main() {
    int fd = open("/dev/some_vuln_device", O_RDWR);
    if (fd < ) {
        perror("open");
        return 1;
    }

    // Send out-of-bounds data structure to cause kernel bug
    char exploit_buffer[1024];
    memset(exploit_buffer, 'A', sizeof(exploit_buffer));
    // Optionally: place carefully crafted data at certain offsets

    // Trigger vulnerability
    int ret = ioctl(fd, VULN_IOCTL_CMD, exploit_buffer);
    if (ret < ) {
        perror("ioctl");
    }

    close(fd);
    return ;
}

Note: In an actual exploit, the attacker would tune the buffer precisely, study the memory layout, and possibly chain multiple bugs. This is *not* a working exploit, but illustrates the pattern.

Tamper with OS updates

Most attackers would need you to install a malicious app or use some other trick to run their code in the first place. However, privilege escalation bugs in the kernel are among the most dangerous on any operating system.

Mitigation and Protection

- Keep Your Device Updated: Google and device vendors patch serious kernel bugs as soon as possible. Go to *Settings → System → Software update* and make sure you have the latest security patches (especially anything dated 2022 or newer).

Don't Sideload Unknown Apps: Only install trusted apps from official stores.

- Check Vendor Advisories: Your device model may have a vendor-specific patch advisory, for example:
 - Google Android Security Bulletins

References & Resources

- Official CVE Record: CVE-2022-20120
- Android Security Bulletin (search for A-203213034)
- General Android Kernel Exploitation
- Understanding Android Privilege Escalation

In Summary

CVE-2022-20120 is an example of how kernel bugs can open the door for attackers to take full control of your device. The good news: patches are usually available quickly, and you’re protected as long as you keep your device updated and don’t install apps from untrusted sources.

Always stay informed, update regularly, and if you’re a developer, consider learning more about kernel security—it’s one of the most exciting, and important, parts of system hacking and defense.


*If you found this write-up helpful, share it with your friends to help keep everyone safer!*

Timeline

Published on: 05/10/2022 21:15:00 UTC
Last modified on: 05/17/2022 13:14:00 UTC