CVE-2021-47518 is a vulnerability identified in the Linux kernel's NFC (Near Field Communication) subsystem, specifically within the netlink callback function nfc_genl_dump_ses_done(). The issue arises because this callback does not verify whether its received argument is non-NULL before dereferencing it. This argument's allocation can fail earlier in the dumpit() function (nfc_genl_dump_ses()), potentially leading to a NULL pointer dereference. Such a flaw can cause the kernel to crash or behave unpredictably, resulting in a denial of service (DoS). The vulnerability is rooted in improper error handling and lack of defensive programming in the NFC netlink interface. While the vulnerability does not appear to have known exploits in the wild, it affects Linux kernel versions identified by the commit hash ac22ac466a659f1b2e02a2e2ee23fc5c42da2c95 and potentially other versions incorporating this code. The fix involves adding a NULL check in the nfc_genl_dump_ses_done() function to prevent dereferencing a NULL pointer. This vulnerability is significant because the Linux kernel is widely used across servers, desktops, and embedded devices, and NFC functionality is increasingly common in various hardware platforms. However, exploitation requires triggering the NFC netlink interface, which may limit the attack surface to systems with NFC enabled and accessible to an attacker.

For European organizations, the impact of CVE-2021-47518 primarily revolves around potential denial of service conditions on Linux systems with NFC enabled. This could disrupt services or applications relying on NFC communication, such as contactless payment systems, access control, or device pairing. Critical infrastructure or industrial control systems using Linux with NFC capabilities could experience operational interruptions. While the vulnerability does not directly lead to privilege escalation or data leakage, the resulting kernel crash could cause system downtime, impacting business continuity. Organizations in sectors like finance, transportation, healthcare, and manufacturing that deploy Linux-based NFC-enabled devices may face increased risk. Additionally, the lack of known exploits reduces immediate threat but does not eliminate the risk of future exploitation, especially if attackers develop targeted methods to trigger the flaw remotely or locally. The impact is mitigated somewhat by the requirement that NFC functionality be active and accessible, which is not universal across all Linux deployments.

To mitigate CVE-2021-47518, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from their Linux distribution vendors. 2) Audit and disable NFC functionality on Linux systems where it is not required, reducing the attack surface. 3) Implement strict access controls and network segmentation to limit exposure of NFC-related interfaces, especially the netlink interface, to untrusted users or processes. 4) Monitor system logs and kernel messages for unusual crashes or errors related to NFC operations, enabling early detection of exploitation attempts. 5) For critical systems, consider deploying kernel live patching solutions to apply fixes without downtime. 6) Educate system administrators about this vulnerability and the importance of maintaining updated kernels and minimizing unnecessary kernel subsystems.