CVE-2022-48938 is a vulnerability identified in the Linux kernel's CDC-NCM (Communications Device Class - Network Control Model) driver, which handles USB network communication. The flaw arises from improper sanity checking of fragment offsets and lengths during data processing. Specifically, a broken or malicious USB device can provide an extreme offset value (e.g., 0xFFF0) combined with a reasonable fragment length. The current sanity check implementation does not properly handle integer overflow conditions when calculating offset + length, allowing the overflow to bypass the intended validation. This occurs because the offset and offset + length calculations are not checked in a manner that prevents overflow, and the values are not treated as unsigned integers. As a result, an attacker controlling a malicious USB CDC-NCM device could exploit this vulnerability to cause unexpected behavior in the kernel, potentially leading to memory corruption, denial of service (kernel panic), or other undefined behavior. The vulnerability has been addressed by ensuring both offset and offset + length are checked to prevent overflow and by treating these quantities as unsigned values. The vulnerability affects multiple versions of the Linux kernel as indicated by the affected commit hashes, and no known exploits are currently reported in the wild. No CVSS score has been assigned yet, and no patch links are provided in the data, but the issue is publicly disclosed and marked as published as of August 22, 2024.

For European organizations, the impact of CVE-2022-48938 depends on their use of Linux systems that interact with USB CDC-NCM devices, such as embedded systems, network appliances, or workstations with USB network adapters. Exploitation could lead to kernel crashes causing denial of service, potentially disrupting critical services or operations. In more severe cases, if memory corruption is triggered, it could be leveraged for privilege escalation or arbitrary code execution, compromising system confidentiality and integrity. Given the Linux kernel's widespread use across servers, desktops, and IoT devices in Europe, organizations relying on USB network devices or embedded Linux systems are at risk. Industrial control systems or telecommunications infrastructure using Linux with CDC-NCM devices could be particularly sensitive. The absence of known exploits reduces immediate risk, but the vulnerability's nature suggests that attackers with physical or USB access could exploit it. This elevates the threat in environments with less physical security or where USB devices are frequently connected. The impact on availability is the most immediate concern, with potential secondary impacts on confidentiality and integrity if exploitation extends beyond denial of service.

To mitigate CVE-2022-48938, European organizations should: 1) Apply the latest Linux kernel updates as soon as patches become available from trusted sources or distributions, ensuring the CDC-NCM driver includes the overflow checks. 2) Restrict physical access to systems to prevent unauthorized USB device connections, especially in sensitive environments. 3) Implement USB device whitelisting or disable unused USB ports to reduce attack surface. 4) Monitor kernel logs for unusual CDC-NCM related errors or crashes that may indicate attempted exploitation. 5) For embedded or specialized devices, coordinate with vendors to obtain firmware or kernel updates addressing this vulnerability. 6) Conduct security audits of USB device usage policies and educate users about risks of connecting untrusted USB devices. 7) Consider deploying kernel hardening features such as Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce exploitation likelihood. These steps go beyond generic advice by focusing on controlling USB device access and ensuring timely patching of the specific kernel component involved.