CVE-2021-47248 is a vulnerability identified in the Linux kernel's UDP networking implementation. The issue arises from a race condition between the close() system call and the udp_abort() function. Both functions attempt to acquire the socket lock, but the problem occurs because udp{v6}_destroy_sock() releases the socket lock before performing destructive actions on the socket. This timing gap allows udp_abort() to act concurrently, leading to a race condition that can cause a kernel panic in the udp_lib_lookup() function. The root cause is that udp_abort() may perform operations on a socket that is in the process of being closed and destroyed, which can lead to use-after-free or other memory corruption issues. The fix implemented uses the SOCK_DEAD flag to prevent udp_abort() from performing any actions when this critical race condition occurs, rather than trying to extend the socket lock scope, which is not feasible. This vulnerability was reported and diagnosed by Kaustubh Pandey and has been addressed in recent Linux kernel updates. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a risk primarily to systems running vulnerable Linux kernel versions, especially those handling UDP network traffic extensively, such as servers, network appliances, and embedded devices. Exploitation could lead to kernel panics causing denial of service (DoS), potentially disrupting critical services and operations. While no known exploits exist currently, the vulnerability could be leveraged in targeted attacks to destabilize systems or as a stepping stone for further kernel-level exploits. Organizations relying on Linux-based infrastructure for networking, cloud services, or industrial control systems could face operational interruptions. The impact on confidentiality and integrity is limited unless combined with other vulnerabilities, but availability is significantly affected due to potential system crashes.

European organizations should prioritize updating their Linux kernels to the latest patched versions that include the fix for CVE-2021-47248. Since the vulnerability involves kernel-level race conditions, applying vendor-provided kernel patches is the most effective mitigation. For environments where immediate patching is not feasible, organizations should monitor UDP socket usage and system logs for unusual kernel panics or crashes. Network segmentation and limiting exposure of critical Linux systems to untrusted networks can reduce attack surface. Additionally, employing kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Control Flow Integrity (CFI) can help mitigate exploitation risks. Regular backups and robust incident response plans should be in place to recover quickly from potential DoS incidents caused by exploitation attempts.