CVE-2022-49273 is a vulnerability identified in the Linux kernel's RTC (Real-Time Clock) driver for the ARM PrimeCell PL031 device. The issue arises from a null pointer dereference caused by improper handling of the RTC alarm feature bit. Specifically, when the system lacks an interrupt line, the RTC alarm feature is disabled. However, the kernel code erroneously clears the RTC_FEATURE_ALARM bit before the allocation of the rtc device structure (ldata->rtc), leading to a null pointer dereference. This flaw can cause the kernel to crash or behave unpredictably when the affected RTC driver is accessed, potentially resulting in a denial of service (DoS) condition. The vulnerability is rooted in the sequence of operations within the driver initialization, where clearing the alarm feature bit should only occur after the rtc device has been properly allocated. The fix involves reordering the code to clear the RTC_FEATURE_ALARM bit only after the rtc device allocation is complete, thereby preventing the null pointer dereference. This vulnerability affects Linux kernel versions containing the faulty commit identified by the hash d9b0dd54a1943f47a381a474f8ea2c94466110c0. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet. The vulnerability primarily impacts systems using the PL031 RTC driver, which is common in ARM-based embedded systems and some server or IoT devices running Linux. While the vulnerability does not allow for privilege escalation or arbitrary code execution, the resulting kernel crash can disrupt system availability and stability.

For European organizations, the impact of CVE-2022-49273 depends largely on the deployment of Linux systems utilizing the PL031 RTC driver, typically found in ARM-based embedded devices, industrial control systems, and certain IoT environments. Organizations relying on such devices for critical infrastructure, manufacturing automation, or telecommunications could experience service interruptions or system downtime if the vulnerability is triggered. Although the vulnerability does not directly compromise confidentiality or integrity, the denial of service caused by kernel crashes can disrupt business operations, leading to potential financial losses and operational delays. In sectors such as healthcare, energy, and transportation, where embedded Linux devices are prevalent, this could affect safety-critical systems. The lack of known exploits reduces immediate risk, but the vulnerability's presence in kernel code means that attackers with local access or the ability to interact with the RTC driver could potentially trigger system crashes. European organizations with large-scale deployments of ARM-based Linux devices should assess their exposure and prioritize patching to maintain system reliability and availability.

To mitigate CVE-2022-49273, European organizations should: 1) Identify all Linux systems running kernels that include the vulnerable PL031 RTC driver, focusing on ARM-based embedded devices and IoT systems. 2) Apply the official Linux kernel patches that reorder the clearing of the RTC_FEATURE_ALARM bit to occur after rtc device allocation. If vendor-specific kernel updates are used, ensure they incorporate this fix. 3) For systems where immediate patching is not feasible, consider disabling the RTC alarm feature if it is not required, to reduce the attack surface. 4) Implement monitoring to detect kernel crashes or system reboots that may indicate exploitation attempts. 5) Restrict local access to vulnerable devices and limit user permissions to prevent unauthorized interactions with the RTC driver. 6) Maintain an inventory of embedded devices and ensure firmware and kernel updates are part of regular maintenance cycles. 7) Engage with device vendors to confirm patch availability and deployment timelines for affected hardware. These steps go beyond generic advice by focusing on embedded and ARM-based Linux environments, which are the primary affected systems.