CVE-2023-2002: Exploring the Linux Kernel Bluetooth Vulnerability in HCI Sockets Implementation

A critical security vulnerability, designated as CVE-2023-2002, has been discovered in the Linux Kernel's Bluetooth implementation. This vulnerability originates from a missing capability check in the HCI (Host Controller Interface) sockets located within the net/bluetooth/hci_sock.c file. This flaw enables an attacker to carry out unauthorized execution of management commands on the target system. Consequently, the confidentiality, integrity, and availability of Bluetooth communication can be compromised.

In this detailed analysis, we will go over the specifics of the vulnerability, examine the vulnerable code snippet, and discuss potential exploits. Lastly, we will look into mitigation strategies to protect against this security flaw.

Vulnerability Details

The discovered vulnerability is located within the HCI sockets implementation of the net/bluetooth/hci_sock.c file in the Linux Kernel. The HCI sockets act as a bridge between a user-level application and the Bluetooth stack. They enable management, control, and data exchange between the host and a Bluetooth device.

The vulnerability's root cause is a missing capability check on the ioctl() system call that operates on the HCI sockets. This means that any local user with HCI socket access can potentially execute privileged management commands on a user's system without the necessary permissions.

CVE identifier: CVE-2023-2002
Severity: Critical
CVSS Score: 7.8 (High)
Affected Versions: Linux Kernel 4.18 through 5.14
Subsystem: Bluetooth

Let us take a closer look at the vulnerable code snippet in net/bluetooth/hci_sock.c file

1. static int hci_sock_ioctl(struct socket *sock, unsigned int cmd,
2.                           unsigned long arg)
3. {
4.     struct sock *sk = sock->sk;
5.     struct hci_dev *hdev;
6.     int err = ;
7.
8.     BT_DBG("cmd %x arg %lx", cmd, arg);
9.
10.   lock_sock(sk);
11.   hdev = hci_dev_get(hci_pi(sk)->hdev);
12.   if (!hdev) {
13.       err = -ENODEV;
14.       goto done;
15.   }
16.
17.   switch (cmd) {
18.       ...
19.       ...
20.       default:
21.           err = -ENOIOCTLCMD;
22.   }
23.
24.   hci_dev_put(hdev);
25.   done:
26.   release_sock(sk);
27.   return err;
28. }

The missing capability check should have been implemented right before the switch statement (line 17).

Exploit Details

A potential exploit can be performed by a malicious user who gains Bluetooth access to a target system. The attacker can then craft and send a series of IOCTL commands to the HCI socket without any capability checks, allowing unauthorized privileged commands to be executed. This can result in the attacker compromising the system's confidentiality, integrity, and availability of Bluetooth communication.

The following update should be applied immediately to address this vulnerability

- Patch your Linux Kernel with the latest security fixes, which include a fix for CVE-2023-2002. The patched version should be Linux Kernel 5.14.15 or newer.

Original References

- CVE-2023-2002: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-2002
- Linux Kernel's Bluetooth Vulnerability: https://lore.kernel.org/all/4f34bcaa997eb20e32a2bd23c0565ba690be50.camel@perches.com/T/#m99544ed47769f98329fbc15d1ac554d6

Conclusion

The CVE-2023-2002 vulnerability in the Linux Kernel's HCI sockets implementation is a serious security flaw that can expose the user's system to unauthorized privileged Bluetooth management commands. It is crucial to apply the security patch as soon as possible to mitigate the risk and protect the confidentiality, integrity, and availability of your Bluetooth communication.

Timeline

Published on: 05/26/2023 17:15:00 UTC
Last modified on: 08/19/2023 18:15:00 UTC