CVE-2021-46924 is a vulnerability identified in the Linux kernel's NFC subsystem, specifically within the st21nfca driver responsible for interfacing with NFC hardware over I2C. The issue arises from a memory leak caused by improper error handling during the device probe and removal processes. When the device probe function allocates memory for 'phy->pending_skb' (a socket buffer), it fails to free this memory if an error occurs or when the device is removed. This results in unreferenced memory objects accumulating over time, which can degrade system performance and stability. The vulnerability is rooted in the kernel's failure to release allocated resources under error conditions, leading to resource exhaustion. The technical details include a backtrace showing the allocation path through __kmalloc_node_track_caller, kmalloc_reserve, __alloc_skb, and the st21nfca_hci_i2c_probe function. The fix involves ensuring that 'pending_skb' is properly freed in both error and removal paths, preventing the leak. This vulnerability affects specific Linux kernel versions identified by the provided commit hashes. There are no known exploits in the wild, and no CVSS score has been assigned yet.

For European organizations, the impact of this vulnerability is primarily related to system reliability and availability. Systems running affected Linux kernel versions with NFC hardware using the st21nfca driver may experience gradual memory leaks leading to increased memory consumption, potential system slowdowns, or crashes if the leak is severe and persistent. This can disrupt services relying on NFC functionality, such as contactless payment systems, access control, or secure authentication mechanisms. While this vulnerability does not directly lead to privilege escalation or data leakage, the resulting denial of service through resource exhaustion can impact critical infrastructure and business operations. Organizations with embedded Linux devices or IoT deployments using NFC may be particularly vulnerable. Given the lack of known exploits, the immediate risk is low, but unpatched systems could become targets for attackers aiming to degrade system availability.

To mitigate this vulnerability, European organizations should: 1) Identify and inventory all Linux systems using NFC hardware with the st21nfca driver, particularly those running affected kernel versions. 2) Apply the official Linux kernel patches that fix the memory leak by ensuring 'pending_skb' is freed in error and removal paths. If official patches are not yet available, consider backporting the fix or upgrading to a kernel version that includes the patch. 3) Monitor system memory usage and logs for signs of memory leaks or abnormal resource consumption related to NFC device probing. 4) Implement proactive system restarts or resource cleanup procedures for embedded devices where patching is delayed. 5) Restrict access to NFC hardware interfaces to trusted users and processes to reduce the risk of triggering the vulnerability through malformed device interactions. 6) Engage with hardware vendors to confirm compatibility and patch availability for embedded devices. These steps go beyond generic advice by focusing on NFC-specific hardware and driver considerations and emphasizing proactive monitoring and inventory management.