CVE-2024-46794 is a vulnerability identified in the Linux kernel specifically affecting the x86 architecture's Trusted Domain Extensions (TDX) implementation. The vulnerability arises in the mmio_read() function, which is responsible for reading memory-mapped I/O (MMIO) data by making a TDVMCALL to the Virtual Machine Monitor (VMM). The issue is that mmio_read() unintentionally exposes the value of an initialized stack variable named 'val' to the VMM. This variable 'val' is used solely as an output parameter and should not have been passed to the VMM in its original state. As a result, the VMM can potentially observe residual data from the kernel stack that was never meant to be shared, leading to a data leak. This exposure could allow a malicious or compromised VMM to gain access to sensitive kernel memory contents, which may include cryptographic keys, passwords, or other confidential information residing temporarily on the stack. The vulnerability was addressed by modifying the mmio_read() function to ensure that the original value of 'val' is not sent to the VMM, thereby preventing unintended data disclosure. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability is limited to Linux kernel versions containing the affected commit (indicated by the hash 31d58c4e557d46fa7f8557714250fb6f89c941ae), and it specifically impacts systems utilizing TDX technology on x86 platforms.

For European organizations, the impact of CVE-2024-46794 depends largely on their use of Linux systems with TDX-enabled x86 processors, which are typically found in environments employing hardware-based virtualization and trusted execution technologies for enhanced security. The data leak could compromise confidentiality by exposing sensitive kernel stack data to the VMM, which might be controlled by an attacker or a compromised hypervisor. This could lead to further privilege escalation or lateral movement within virtualized environments. Organizations relying on TDX for secure cloud workloads, confidential computing, or multi-tenant virtualization could face increased risks of data breaches or intellectual property theft. However, the vulnerability does not directly affect system availability or integrity unless combined with other exploits. Since no active exploitation is reported, the immediate risk is moderate but could escalate if attackers develop exploits. The impact is more pronounced for sectors handling sensitive data such as finance, government, healthcare, and critical infrastructure, where confidentiality breaches can have severe regulatory and reputational consequences.

European organizations should prioritize patching Linux kernels to the fixed versions that address CVE-2024-46794 as soon as updates become available from their Linux distribution vendors. Specifically, they should: 1) Identify and inventory all Linux systems running on x86 platforms with TDX enabled, focusing on servers and virtualized environments. 2) Apply kernel updates or patches that remove the data leak in mmio_read() promptly. 3) Review and harden the security of the VMM/hypervisor layer to limit the risk of compromise, including strict access controls and monitoring for suspicious activity. 4) Employ runtime security tools that can detect anomalous behavior in virtualized environments. 5) For cloud providers and enterprises using confidential computing, validate that their hardware and software stacks are updated and compliant with security advisories. 6) Conduct security audits and penetration testing focusing on virtualization security to identify potential exploitation paths. 7) Implement strict separation of duties and least privilege principles for administrators managing virtualized infrastructure to reduce insider threat risks.