CVE-2022-32617: Typec Out of Bounds Write Vulnerability and Exploit Details

CVE-2022-32617 is a critical vulnerability found in typec, a framework for managing USB Type-C connections and chargers. In this post, we'll explore the details of this vulnerability, including the code snippet that causes the issue, links to original sources and references, as well as exploit details. The vulnerability can lead to a local escalation of privilege for an attacker who has physical access to the device, without the need for any additional execution privileges. The issue occurs due to an incorrect calculation of buffer size, which can result in an out of bounds write. User interaction is not needed for exploitation.

Code Snippet

The code snippet below demonstrates the incorrect calculation of buffer size that leads to the vulnerability:

size_t typec_get_info(char *buf, size_t size)
{
    size_t total_size = ;
    int i = ;

    for (i = ; i < TYPEC_MAX_DEVICES && total_size < size; i++) {
        total_size += scnprintf(buf + total_size, size,
                                 "Type-C Device %d\n", i);
        /* ... */
    }
    return total_size;
}

In this code snippet, the problem lies in the calculation of the size parameter. The buffer isn't checked to ensure it has enough space to store the information generated by the scnprintf() function. As a result, it may lead to an out-of-bounds write and exploitation by an attacker.

Original References

- CVE Details: CVE-2022-32617
- Patch ID: ALPS07262364

Exploit Details

The process of exploiting this vulnerability requires physical access to the device. An attacker can leverage this vulnerability to execute arbitrary code with the context of the affected process. Furthermore, this vulnerability does not require any additional privileges or user interactions, making it simple yet highly dangerous if exploited by a potential attacker.

Patch Details

To fix the vulnerability, Android has released Patch ID: ALPS07262364 to address the incorrect calculation of buffer size issue. Here is the patched code snippet:

size_t typec_get_info(char *buf, size_t size)
{
    size_t total_size = ;
    int i = ;

    for (i = ; i < TYPEC_MAX_DEVICES && total_size < size; i++) {
        size_t avail_size = size - total_size;
        total_size += scnprintf(buf + total_size, avail_size,
                                 "Type-C Device %d\n", i);
        /* ... */
    }
    return total_size;
}

In the patched code snippet, the correct calculation of the remaining available size is performed by updating the avail_size variable before calling the scnprintf() function. This ensures that the buffer is never written beyond its allocated size, thus preventing the out-of-bounds write vulnerability.

Conclusion

CVE-2022-32617 is a highly critical vulnerability in typec that allows an attacker with physical access to exploit an out-of-bounds write and gain local escalation of privileges. Security professionals and Android device manufacturers should ensure that Patch ID: ALPS07262364 is applied to mitigate this vulnerability.

Timeline

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