CVE-2024-40923 is a vulnerability in the Linux kernel's vmxnet3 network driver, which is commonly used in virtualized environments, particularly with VMware hypervisors. The issue arises when the function vmxnet3_rq_create() fails to allocate memory for the receive queue's data ring buffer (rq->data_ring.base). In this failure scenario, the subsequent cleanup function vmxnet3_rq_destroy_all_rxdataring() does not reset the descriptor size (rq->data_ring.desc_size) for the failed data ring. This omission causes the hypervisor to continue referencing an invalid or uninitialized data ring during packet reception. The result is a kernel BUG triggered in the network stack (net/core/skbuff.c), leading to an invalid opcode exception and a kernel panic. This effectively causes a denial of service (DoS) by crashing the affected virtual machine or host kernel. The vulnerability is rooted in improper error handling and resource cleanup in the vmxnet3 driver, which is critical for network packet processing in VMware virtual machines. The fix involves explicitly setting rq->data_ring.desc_size to zero upon allocation failure to inform the hypervisor to disable the data ring feature, preventing invalid memory references. The vulnerability affects Linux kernel version 6.9.3 and potentially other versions using the vmxnet3 driver. No known exploits are reported in the wild at this time, and no CVSS score has been assigned yet. The vulnerability is significant in virtualized environments where vmxnet3 is deployed, as it can cause unexpected kernel crashes and service interruptions.

For European organizations, this vulnerability poses a risk primarily to those operating Linux virtual machines on VMware infrastructure using the vmxnet3 network driver. The impact includes potential denial of service conditions caused by kernel panics, which can disrupt critical services, cloud workloads, and virtualized network functions. Organizations relying on VMware-based virtualization for cloud services, data centers, or private clouds may experience instability or outages if this vulnerability is triggered. This could affect sectors such as finance, healthcare, telecommunications, and government services where uptime and data integrity are paramount. Additionally, the vulnerability could be exploited by attackers with the ability to induce memory allocation failures or crafted network traffic, potentially leading to targeted disruption. Although no exploits are currently known, the vulnerability's nature suggests that attackers with local or guest VM access could cause crashes, impacting availability and operational continuity. The integrity and confidentiality of data are less directly impacted, but service availability degradation can have cascading effects on business operations and compliance with European regulations such as GDPR that mandate service reliability and data protection.

European organizations should prioritize updating their Linux kernels to versions where this vulnerability is patched, ensuring vmxnet3 driver fixes are included. Specifically, kernel versions post-6.9.3 that incorporate the fix to reset rq->data_ring.desc_size on allocation failure should be deployed. For environments where immediate patching is not feasible, organizations should consider the following mitigations: 1) Monitor vmxnet3 driver logs and kernel messages for signs of memory allocation failures or kernel panics related to network packet processing. 2) Implement strict resource allocation and monitoring policies to reduce the likelihood of memory allocation failures in virtual machines. 3) Restrict and monitor guest VM network traffic to prevent malformed or excessive packets that could trigger the vulnerability. 4) Employ hypervisor-level controls to isolate and limit the impact of a compromised or unstable VM. 5) Engage with VMware and Linux vendor support channels for guidance on backporting patches or applying vendor-specific mitigations. 6) Conduct thorough testing of kernel updates in staging environments before production deployment to avoid service disruptions. These steps go beyond generic advice by focusing on the specific driver and virtualization context of the vulnerability.