A NULL pointer dereference vulnerability has been discovered in the Linux Kernel, specifically in the vmxnet3 network driver. This issue has the potential to allow local attackers with normal user privileges to execute a denial of service (DoS) attack on affected systems. This article will discuss the details of the vulnerability, its exploitation, and the available remediation techniques.

Vulnerability Details

The vulnerability is identified as CVE-2023-4459 and is present in the vmxnet3_rq_cleanup function located in the file drivers/net/vmxnet3/vmxnet3_drv.c of the Linux Kernel's networking sub-component. vmxnet3 is a network driver used by VMware virtual machines for high-performance packet processing.

The NULL pointer dereference flaw originates from a missing sanity check during the cleanup process in the vmxnet3_rq_cleanup function. This allows an attacker to exploit this vulnerability and potentially cause a system crash, denying access to legitimate users and services.

Exploit Details

An attacker with local access and normal user privileges can exploit this vulnerability by setting up a specially crafted packet to trigger the NULL pointer dereference flaw in the vmxnet3_rq_cleanup function. Here is a code snippet demonstrating the missing sanity check in the cleanup function:

static void vmxnet3_rq_cleanup(struct vmxnet3_rx_queue *rq,
				unsigned int num_allocated_receiving_bufs)
	struct vmxnet3_adapter *adapter = rq->adapter;
	for (i = ; i < num_allocated_receiving_bufs; i++) {
		if (rbi->skb) {
			vmxnet3_rq_destroy_skb(adapter, rbi); //<-- The problematic function call.

It can be observed from the snippet above that there is no check for 'rbi' being NULL before the call to vmxnet3_rq_destroy_skb(), allowing the NULL pointer dereference to be exploited by a malicious user.

To successfully exploit this vulnerability, an attacker would need to have local access to the target system and use a carefully crafted packet, potentially triggering the NULL pointer dereference, causing a kernel crash and denial of service.

- Linux Kernel Git Repository: vmxnet3 Driver Vulnerable Code
- CVE-2023-4459 - National Vulnerability Database

Mitigation and Remediation

To mitigate the impact of this vulnerability, users are urged to restrict local access to sensitive systems, monitor for any suspicious activity, and perform regular kernel updates to maintain the overall security of their systems. As a long-term solution, software vendors, such as VMware and Linux distributions, should incorporate patches that address the NULL pointer dereference issue once they become available.

As of now, no patch has been released for this vulnerability. It is essential for users to stay informed about any updates or patches that become available and apply them as soon as possible to ensure the protection and security of their systems from potential exploitation.


Published on: 08/21/2023 19:15:00 UTC
Last modified on: 08/24/2023 21:40:00 UTC