In 2022, a serious security vulnerability was discovered in the TypeC (USB-C) kernel driver found in several MediaTek-powered Android devices. This vulnerability, tracked as CVE-2022-32617 (Patch/Issue ID: ALPS07262364), allows a local attacker with physical access to the device to gain higher privileges—without any help from the user. This post breaks down the issue in plain English, presents code snippets, and shows how an attacker could exploit it.

What is CVE-2022-32617?

CVE-2022-32617 refers to an out-of-bounds write bug in the TypeC kernel driver. The bug is rooted in a simple, but critical, coding mistake: the driver fails to properly validate the size of a buffer before writing to it. This allows an attacker to overwrite memory that they should not be able to access.

Potentially execute malicious code in the kernel context

Since the bug requires only physical access, it is attractive for attackers who might get their hands on the device, such as during repair, theft, or temporary access situations.

Where's the Problem?

The bug resides in the way the driver calculates the size of a data buffer. For example, when processing input from a USB-C device or cable, the driver copies user-supplied data into a fixed-size buffer without verifying the size.

Here is a simplified pseudo-code showing the problematic logic (not the exact code)

#define TYPEC_BUF_SIZE 64

void handle_typec_message(char *input, size_t len) {
    char buffer[TYPEC_BUF_SIZE];
    
    // Vulnerable: No check if 'len' > TYPEC_BUF_SIZE
    memcpy(buffer, input, len);
}

What's wrong?
If len is greater than TYPEC_BUF_SIZE (64 bytes), memcpy will overwrite memory past the buffer's end. This can corrupt adjacent memory, leading to unexpected kernel behavior.

Here’s a basic outline of how an attacker could take advantage of CVE-2022-32617

1. Obtain Physical Access: The attacker gets their hands on a vulnerable device—no root or other permissions required.
2. Connect Malicious USB-C Peripheral: The attacker attaches a specially crafted USB-C device or cable that sends a payload longer than 64 bytes.
3. Trigger the Vulnerability: The kernel driver processes the malicious data, resulting in out-of-bounds memory corruption.

Gain kernel-level code execution or escalate privileges

The attack does not require user interaction—just plugging in the device is enough.

Example Exploit Snippet

This is a conceptual Python script that could run on an external microcontroller to send large packets:

data = b"A" * 128  # 128 bytes, double the buffer
with open("/dev/usb_typec", "wb") as usb:
    usb.write(data)

*Note: The actual exploit would depend on the specific device and hardware, but the idea is to send oversized input that the driver will mishandle.*

The patch with ID ALPS07262364 simply adds the missing length check, for example

void handle_typec_message(char *input, size_t len) {
    char buffer[TYPEC_BUF_SIZE];

    if (len > TYPEC_BUF_SIZE) {
        // Reject or truncate input
        len = TYPEC_BUF_SIZE;
    }
    memcpy(buffer, input, len);
}

By ensuring the copy never exceeds the buffer, the risk is eliminated.

Android devices using certain MediaTek chipsets

- Devices with unpatched kernels and drivers from before the fix (Android security bulletins from summer 2022 and earlier may be affected)

Are You Protected?

If your device is running OEM firmware released after July 2022, or has the patch with ID ALPS07262364, you're safe.
To check: Go to Settings > About > Security Patch Level.

References and Further Reading

- NIST NVD entry for CVE-2022-32617
- MediaTek Security Bulletin
- Android Security Bulletin – July 2022
- Common Out-of-Bounds Write Mistakes in Drivers
- Patch ALPS07262364 (example URL)

Conclusion

CVE-2022-32617 is a good example of how a small coding mistake—a missing size check—can lead to a big security risk. If you use an Android device with a MediaTek chip, make sure your system is up to date. Physical attacks through USB ports remain a serious threat, but patches are available and should be installed without delay.

Timeline

Published on: 11/08/2022 21:15:00 UTC
Last modified on: 11/09/2022 16:07:00 UTC