CVE-2022-33985 is a high-severity vulnerability involving a Time-Of-Check to Time-Of-Use (TOCTOU) race condition in the handling of Direct Memory Access (DMA) transactions targeting input buffers used by the NvmExpressDxe software System Management Interrupt (SMI) handler. The NvmExpressDxe driver is part of the UEFI firmware stack responsible for managing NVMe storage devices during system boot. The vulnerability arises because DMA transactions can manipulate input buffers in a way that causes corruption of the System Management RAM (SMRAM), a highly privileged and isolated memory region used by the System Management Mode (SMM) of the CPU. SMM operates at a higher privilege level than the operating system, and corruption of SMRAM can lead to arbitrary code execution with elevated privileges, compromising system confidentiality, integrity, and availability. The issue was discovered by Insyde engineering based on Intel's iSTARE group findings and affects multiple kernel versions, with fixes released for kernel versions 5.2, 5.3, 5.4, and 5.5. The vulnerability is characterized by a CVSS v3.1 score of 7.0, indicating high severity, with attack vector local (AV:L), requiring high attack complexity (AC:H), low privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Exploitation requires local access and the ability to perform DMA transactions targeting the vulnerable buffers, which could be possible via malicious peripherals or compromised devices. No known exploits in the wild have been reported to date. The root cause is a race condition in the software SMI handler's input buffer processing, allowing an attacker to manipulate the timing of DMA transactions to corrupt SMRAM contents. This vulnerability falls under CWE-367 (Time-of-check Time-of-use Race Condition).

For European organizations, the impact of CVE-2022-33985 can be significant, especially for enterprises and critical infrastructure relying on systems with vulnerable UEFI firmware and kernel versions. Successful exploitation could allow attackers to execute arbitrary code at the highest privilege level, bypassing operating system security controls, potentially leading to persistent firmware-level malware infections, data exfiltration, or disruption of critical services. This is particularly concerning for sectors such as finance, healthcare, energy, and government, where confidentiality and system integrity are paramount. Since the vulnerability involves SMRAM corruption via DMA, systems with peripheral devices capable of DMA (e.g., Thunderbolt, PCIe devices) are at higher risk. The attack requires local access or the ability to connect malicious hardware, which may limit remote exploitation but raises concerns about insider threats or supply chain attacks involving compromised devices. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, as attackers may develop exploits over time. European organizations using affected kernel versions or firmware should consider this vulnerability a serious threat to system security and operational continuity.

To mitigate CVE-2022-33985, European organizations should: 1) Apply firmware and kernel updates provided by vendors promptly, specifically updating to patched kernel versions 5.2: 05.27.25, 5.3: 05.36.25, 5.4: 05.44.25, or 5.5: 05.52.25 or later. 2) Restrict or disable DMA access from untrusted or unnecessary peripheral devices, employing Input-Output Memory Management Unit (IOMMU) protections to isolate DMA transactions and prevent unauthorized memory access. 3) Implement strict physical security controls to prevent unauthorized local access or connection of malicious hardware devices capable of DMA. 4) Monitor system firmware integrity using tools that verify UEFI firmware and SMRAM integrity to detect potential corruption or tampering. 5) Employ endpoint detection and response (EDR) solutions capable of detecting anomalous behavior indicative of firmware-level compromise. 6) Coordinate with hardware vendors to ensure firmware updates include robust protections against TOCTOU race conditions in SMI handlers. 7) Educate IT and security staff about the risks of DMA attacks and the importance of controlling peripheral device access. These measures go beyond generic patching advice by emphasizing hardware-level protections and operational controls to reduce the attack surface.