CVE-2021-47194 is a vulnerability in the Linux kernel's cfg80211 wireless configuration subsystem. The issue arises when userspace tools switch the wireless interface type from P2P Group Owner (NL80211_IFTYPE_P2P_GO) to Ad-Hoc mode (NL80211_IFTYPE_ADHOC) using the netlink command NL80211_CMD_SET_INTERFACE. During this transition, the kernel fails to invoke the cleanup function cfg80211_stop_ap(), which is responsible for properly stopping the access point and cleaning up associated data structures. As a result, certain internal kernel data structures, specifically sdata->assigned_chanctx_list, are re-initialized while still linked in the assigned_vifs list. This leads to corruption of linked lists managing virtual interfaces and channel contexts. Such corruption can cause undefined behavior within the kernel, including potential memory corruption, kernel crashes (denial of service), or other stability issues. The vulnerability affects multiple Linux kernel versions identified by the commit hash ac800140c20e7ae51117e71289065bedd4930fc2. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The flaw is rooted in improper resource cleanup during interface type switching in wireless networking code, which is critical for systems relying on dynamic wireless interface management.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with wireless networking capabilities, especially those that utilize P2P (peer-to-peer) wireless modes or dynamically switch wireless interface types. The impact includes potential kernel instability or crashes, which can lead to denial of service on affected devices. This can disrupt critical infrastructure, enterprise wireless networks, or embedded systems relying on Linux-based wireless connectivity. Organizations in sectors such as telecommunications, manufacturing, transportation, and public services that use Linux-based wireless access points or IoT devices could face operational disruptions. Although no remote code execution or privilege escalation is directly indicated, the kernel memory corruption could be leveraged in complex attack chains. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed promptly to prevent future exploitation. The impact on confidentiality and integrity is limited but availability could be significantly affected if the kernel crashes or becomes unstable.

To mitigate this vulnerability, European organizations should: 1) Apply the latest Linux kernel patches that address CVE-2021-47194 as soon as they become available from their Linux distribution vendors or upstream kernel sources. 2) Audit and restrict the use of wireless interface type switching in userspace tools, especially transitions involving P2P_GO to ADHOC modes, to minimize triggering the vulnerable code path. 3) Implement monitoring for kernel crashes or unusual wireless interface behavior that could indicate exploitation attempts. 4) For critical systems, consider isolating wireless interfaces or using hardened kernel configurations that limit dynamic interface changes. 5) Engage with vendors of embedded Linux devices to ensure firmware updates include the fix. 6) Conduct thorough testing of wireless networking functionality after patching to confirm stability. These steps go beyond generic advice by focusing on controlling interface switching behavior and proactive monitoring in addition to patching.