CVE-2021-47252 is a vulnerability identified in the Linux kernel specifically related to the batman-adv (Better Approach To Mobile Adhoc Networking - advanced) module, which is used for mesh networking. The issue arises from the handling of Originator Message (OGM) packets within the soft/batadv interface. During the queuing and transmission process of an OGM, the interface can be changed, leading to a timing-related inconsistency. The vulnerability is primarily about the misuse of WARN_ON, a kernel macro intended to flag serious kernel bugs, which in this case was used to report timing-related warnings that should instead be logged with pr_warn. Although the vulnerability does not directly describe a memory corruption or privilege escalation, the timing inconsistency and improper warning mechanism could potentially lead to kernel instability or unexpected behavior in the batman-adv mesh networking functionality. This could affect systems relying on batman-adv for network routing and communication, especially in environments where mesh networking is critical. The vulnerability has been resolved by correcting the warning usage and addressing the timing issue to prevent the interface from changing during OGM transmission. No known exploits are currently reported in the wild, and the vulnerability does not have an assigned CVSS score. The affected versions are identified by a specific git commit hash, indicating the issue is in a particular state of the Linux kernel source code prior to the patch.

For European organizations, the impact of CVE-2021-47252 depends largely on their use of Linux systems running the batman-adv module, which is common in mesh networking scenarios such as community networks, IoT deployments, and certain industrial or research environments. If exploited or triggered, the timing inconsistency could cause kernel warnings or instability, potentially leading to degraded network performance or system crashes. This could disrupt critical communications in sectors relying on mesh networks, including telecommunications, smart city infrastructure, and emergency services. Although no direct exploitation is known, the presence of such a kernel-level issue could be leveraged in complex attack chains to cause denial of service or to aid in privilege escalation if combined with other vulnerabilities. The impact on confidentiality and integrity is limited, but availability could be affected due to potential kernel instability. Given the widespread use of Linux in European IT infrastructure, especially in public sector and technology companies, unpatched systems could face operational risks.

European organizations should ensure that all Linux systems, particularly those utilizing batman-adv for mesh networking, are updated to the latest kernel versions where this vulnerability has been patched. Since the affected versions are identified by specific commit hashes, organizations should track kernel updates from their Linux distribution vendors and apply patches promptly. Network administrators should audit their use of batman-adv and consider alternative routing protocols if mesh networking is not critical or if stability is a concern. Additionally, monitoring kernel logs for WARN_ON messages related to batman-adv can help detect attempts to trigger this condition. For environments with high availability requirements, implementing redundancy and failover mechanisms can mitigate potential disruptions caused by kernel instability. Finally, organizations should maintain a robust patch management process and subscribe to Linux kernel security advisories to stay informed about similar vulnerabilities.