CVE-2023-20954: Critical Out-of-Bounds Write Vulnerability in SDP_AddAttribute of sdp

In this long read post, we will explore a critical security vulnerability identified as CVE-2023-20954. This vulnerability exists in the SDP_AddAttribute function of the sdp_db.cc file, which is part of the Android Bluetooth stack. A possible out-of-bounds write vulnerability may occur due to an incorrect bounds check. Successful exploitation of this vulnerability could allow an attacker to execute remote code without the need for additional permissions or user interaction. This issue affects Android versions 11 through 13, and the Android ID for this vulnerability is A-261867748.

Exploit Details

An out-of-bounds write vulnerability arises when the program incorrectly checks the boundaries of a buffer before writing data. When this occurs, the program may write more data than the buffer can hold, causing critical data to be overwritten in the adjacent memory. This can lead to remote code execution (RCE) where an attacker could potentially execute arbitrary code on the affected device.

In the case of CVE-2023-20954, the vulnerability occurs in the SDP_AddAttribute function of the sdp_db.cc file. The SDP (Service Discovery Protocol) is an important part of the Bluetooth protocol stack which allows devices to discover and interact with services offered by other devices. This function is responsible for adding attribute data to an existing SDP record.

The vulnerability triggers when the function fails to properly check the bounds before adding attribute data to an existing SDP record. Here's an example of the vulnerable code snippet:

int SDP_AddAttribute(SDPDB_HANDLE handle, const uint8_t *p_attr_data, uint16_t attr_len) {
  // ... other code ...

  if (p_rec != NULL && p_rec->attr_count < SDP_MAX_LIST_ELEMS) {
    Attribute* p_attr = &p_rec->attribute[p_rec->attr_count]; // Vulnerable: No proper bounds check for the attribute array.
    p_attr->len = attr_len;
    p_attr->p_value = p_value;
    p_attr->id = id;
    p_rec->attr_count += 1;
  } else {
    // Error handling...
  }

  // ... other code ...
}

The vulnerability can be exploited by an attacker sending a malicious Bluetooth Service Discovery request containing crafted attribute data to the target Android device. Since no user interaction is required, this poses a significant risk to users, as their device may be attacked without their knowledge.

Original References

The information about this vulnerability, including the affected Android versions and the Android ID, can be found in the following Android Security Bulletin:

- Android Security Bulletin—June 2024

Mitigations and Recommendations

To protect yourself from potential attacks exploiting this vulnerability, it is essential to apply the latest Android security patches as soon as they become available for your device. This will ensure that your device has the most up-to-date security protections and reduce the risk of successful exploits.

Additionally, you should only pair your Bluetooth device with known and trusted devices to minimize the risk of receiving malicious service discovery requests from untrusted sources. This can be done by using the Bluetooth settings in your device to configure which devices are allowed to connect to your device.

Conclusion

CVE-2023-20954 is a critical out-of-bounds write vulnerability in the SDP_AddAttribute function of the sdp_db.cc file, which is part of the Android Bluetooth stack. This vulnerability can lead to remote code execution without the need for additional permissions or user interaction. By staying informed about this vulnerability and applying the latest security patches to your Android device, you can help protect yourself from potential attacks exploiting this issue.

Timeline

Published on: 03/24/2023 20:15:00 UTC
Last modified on: 03/29/2023 15:00:00 UTC