CVE-2022-42896 - Critical Use-After-Free Vulnerabilities in Linux Kernel's Bluetooth Subsystem: Risks, Exploits, and Solutions

The Common Vulnerabilities and Exposures (CVE) system has recently assigned the identifier CVE-2022-42896 to a set of critical use-after-free vulnerabilities in the Linux kernel's Bluetooth subsystem. The affected code resides in the net/bluetooth/l2cap_core.c file, specifically within the l2cap_connect and l2cap_le_connect_req functions. These vulnerabilities have the potential to enable a remote attacker to execute malicious code and leak kernel memory over Bluetooth, provided they are within range of the targeted device. In this article, we delve into the technical details of these vulnerabilities, assess their impact, and provide recommendations for remediation and prevention.

Code Snippet

To understand the source of these use-after-free vulnerabilities, it is crucial to examine the relevant code within the l2cap_core.c file:

int l2cap_connect(struct sock *sk)
{
    /* ... */
    struct l2cap_chan *chan = l2cap_pi(sk)->chan;
    /* ... */
    l2cap_send_conn_req(chan);
    /* ... */
}

int l2cap_le_connect_req(struct sock *sk)
{
    /* ... */
    struct l2cap_chan *chan = l2cap_pi(sk)->chan;
    /* ... */
    l2cap_send_le_conn_req(chan);
    /* ... */
}

In the code snippet above, a critical memory management error occurs due to a specific sequence of events, which leads to the use-after-free vulnerability. The functions l2cap_connect and l2cap_le_connect_req create a pointer to the l2cap_chan structure associated with the socket. This pointer is then passed to the l2cap_send_conn_req and l2cap_send_le_conn_req functions that may potentially cause the l2cap_chan structure to be prematurely freed, leading to a dangling pointer. When the code subsequently tries to access this freed memory, the use-after-free vulnerability is triggered.

Exploit Details

An attacker with knowledge of this vulnerability can exploit it remotely by crafting a series of malicious Bluetooth packets designed to trigger the flawed code execution path within the kernel. Once the victim's device accepts the incoming Bluetooth connection, the attacker can obtain a foothold on the system by executing code within the kernel memory, potentially leading to the compromise of the entire device. Furthermore, the attacker can abuse this vulnerability to gain unauthorized access to sensitive kernel memory data, posing severe risks to user privacy and security.

Original References

The discovery of these vulnerabilities can be attributed to the diligent efforts of the Linux kernel development community. The details of the vulnerabilities and the proposed fix were discussed in the following commit:

- Commit: 711f8c3fb3db61897080468586b970c87c61d9e4

Recommendations

To mitigate the risks associated with CVE-2022-42896, we strongly advise users to apply the patch introduced in the aforementioned commit. Linux distribution vendors are expected to incorporate this fix in their upcoming kernel updates. It is of utmost importance for users to stay abreast of the latest security developments and ensure their systems are updated promptly to minimize exposure to these dangerous vulnerabilities.

Conclusion

CVE-2022-42896 highlights the ever-present risks of use-after-free vulnerabilities in software written in low-level languages like C, which do not automatically manage memory allocation and deallocation. It is essential for developers and users alike to remain vigilant about security and take prompt action to address vulnerabilities as they are discovered. By being proactive and keeping software up-to-date, individuals and organizations can bolster their security posture and reduce their risk of compromise.

Timeline

Published on: 11/23/2022 15:15:00 UTC
Last modified on: 03/01/2023 20:15:00 UTC