CVE-2021-47602 is a vulnerability identified in the Linux kernel's mac80211 subsystem, which is responsible for handling wireless networking functions. The vulnerability arises from improper handling of non-QoS (Quality of Service) data frames during admission control processes. Specifically, the kernel code attempted to access the QoS field in the header of all frames, but non-QoS null function packets do not contain this field and are shorter than expected. This leads to the use of uninitialized values, which can cause undefined behavior or potential security issues. The root cause is that admission control logic was not properly restricted to only QoS data frames, resulting in attempts to process frames that lack the necessary QoS header. The fix involves modifying the admission control code to only operate on QoS data packets, thereby preventing access to invalid memory regions or uninitialized data. This vulnerability was reported by Syzbot, an automated kernel fuzzer, 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. The affected versions are identified by specific kernel commit hashes, indicating that the issue is present in certain development or stable branches prior to patching. This vulnerability is technical in nature and relates to the internal packet processing logic of the Linux wireless stack, which could potentially be triggered by crafted wireless frames.

For European organizations, the impact of CVE-2021-47602 depends largely on their use of Linux-based systems with wireless networking capabilities, particularly those relying on the mac80211 subsystem. Since Linux is widely used in servers, embedded devices, IoT, and networking equipment, any device that processes wireless frames using the vulnerable kernel versions could be affected. Potential impacts include system instability, crashes, or denial of service due to the kernel accessing uninitialized memory. Although no direct remote code execution or privilege escalation has been reported, the undefined behavior could be leveraged in complex attack scenarios to disrupt wireless communications or degrade network reliability. This is particularly relevant for critical infrastructure, telecommunications providers, and enterprises with large Linux deployments. The vulnerability could also affect embedded Linux devices used in industrial control systems or smart city applications across Europe. Given the absence of known exploits, the immediate risk is moderate, but organizations should remain vigilant and prioritize patching to prevent future exploitation attempts.

European organizations should take the following specific mitigation steps: 1) Identify all Linux systems using the mac80211 wireless stack, especially those running kernel versions prior to the patch commit referenced in CVE-2021-47602. 2) Apply the latest Linux kernel updates that include the fix restricting admission control to QoS data frames only. 3) For embedded or IoT devices where kernel updates are not straightforward, coordinate with device vendors to obtain patched firmware or consider network segmentation to isolate vulnerable devices. 4) Monitor wireless network traffic for unusual or malformed frames that could attempt to trigger the vulnerability. 5) Implement strict wireless network access controls and use strong authentication to limit exposure to potentially malicious wireless frames. 6) Incorporate this vulnerability into vulnerability management and patching workflows to ensure timely remediation. 7) For critical systems, consider deploying kernel hardening techniques or additional runtime protections to mitigate risks from memory corruption issues.