CVE-2022-42895 - Infoleak Vulnerability in Linux Kernel's Bluetooth L2CAP Core: Understanding the Exploit and Securing Your System

A recent vulnerability, identified as CVE-2022-42895, has been discovered in the Linux kernel. The flaw affects the Bluetooth subsystem and specifically resides in the net/bluetooth/l2cap_core.c's l2cap_parse_conf_req function. This vulnerability can be exploited remotely to leak kernel pointers, potentially exposing sensitive information and making your devices more susceptible to attacks. In this post, we will provide an in-depth analysis of the exploit, relevant code snippets, and recommendations to protect your systems.

Code Snippet

The affected function, l2cap_parse_conf_req, is located in the net/bluetooth/l2cap_core.c file. A code snippet illustrating the vulnerability is provided below:

static inline int l2cap_parse_conf_req(struct l2cap_chan *chan,
                      struct l2cap_conf_req *req, u8 *data)
{
	u16 type, hint, len;
	void *val;

	while (req->dcid) {
		type = le16_to_cpu(data[]);
		hint = le16_to_cpu(data[1]) & L2CAP_CONF_HINT;
		len  = le16_to_cpu(data[1]) & L2CAP_CONF_LENGTH_MASK;
		val  = data + L2CAP_CONF_HDR_SIZE;

		if (len > L2CAP_CONF_MAX_SIZE chan)
			return -EINVAL;

		if (!l2cap_valid_conf_type(type))
			return -EINVAL;

		data += L2CAP_CONF_HDR_SIZE + len;
		req->dcid--;
	}

	return ;
}

As shown in the code snippet above, the l2cap_parse_conf_req function processes the incoming configuration request for the Bluetooth connection. However, it fails to properly validate the length of the configuration data, potentially allowing an attacker to remotely access kernel pointers.

Original References

The vulnerability was first identified and patched in the following Linux kernel commit: https://github.com/torvalds/linux/commit/b1a2cd50c0357f243b7435a732b4e62ba3157a2e

The official CVE description and detailed information can be found at: https://www.google.com/url?q=https://nvd.nist.gov/vuln/detail/CVE-2022-42895

Exploit Details

An attacker exploiting this vulnerability can send a malformed configuration request to a target device, triggering the infoleak. As a result, kernel pointers can be disclosed to the attacker, which can be used to bypass kernel ASLR (Address Space Layout Randomization) or obtain sensitive information that could lead to further compromise.

Recommendations

To secure your system and mitigate this vulnerability, we strongly recommend upgrading your Linux kernel to a version that contains the patch provided in the following commit: https://github.com/torvalds/linux/commit/b1a2cd50c0357f243b7435a732b4e62ba3157a2e

If you run a distribution where upgrading the kernel is difficult, please refer to your distribution's documentation and support channels for further guidance.

Additionally, we advise consistently monitoring your systems for unusual activity and strengthening your general security posture by following best practices, such as regular patching and system updates, access control management, and network segmentation.

Conclusion

CVE-2022-42895 showcases the importance of being diligent and proactive in securing your Linux systems. By understanding vulnerabilities, staying informed on patches, and employing a robust security posture, you will be able to defend against exploitation and keep your systems secure.

Timeline

Published on: 11/23/2022 15:15:00 UTC
Last modified on: 01/23/2023 18:29:00 UTC