CVE-2021-47082 is a vulnerability identified in the Linux kernel's TUN (network tunnel) driver, specifically related to a double free condition in the function tun_free_netdev(). The issue arises from improper memory management where the dev->tstats and tun->security allocations are not correctly handled during the network device registration and destruction lifecycle. The fix involved moving these allocations to a new initialization routine tun_net_init(), which is called by register_netdevice(), ensuring that the paired destructor tun_free_netdev() properly frees resources without causing double free errors. The vulnerability was detected through Kernel Address Sanitizer (KASAN) reports indicating double-free or invalid-free errors in the SELinux security hooks related to the TUN device. The double free can lead to undefined behavior such as kernel crashes, memory corruption, or potential escalation of privileges if exploited. The vulnerability affects Linux kernel versions prior to the patch and is triggered during network device registration and ioctl operations on TUN devices. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability requires local access to the system to trigger the ioctl calls that lead to the double free, implying that an attacker must have some level of user privileges or access to the system to exploit it. The TUN driver is widely used for creating virtual network interfaces, commonly leveraged in VPN solutions and container networking, making this vulnerability relevant for systems running Linux kernels with TUN support enabled.

For European organizations, the impact of CVE-2021-47082 can be significant depending on their reliance on Linux-based infrastructure, particularly those using VPNs, containerized environments, or virtualized network functions that utilize the TUN driver. Exploitation of this vulnerability could lead to kernel crashes causing denial of service, or potentially enable privilege escalation if an attacker can manipulate kernel memory through the double free condition. This could compromise confidentiality, integrity, and availability of critical systems. Organizations in sectors such as finance, telecommunications, government, and critical infrastructure that heavily depend on Linux servers and virtual networking may face operational disruptions or security breaches if the vulnerability is exploited. Although no active exploits are known, the presence of this vulnerability in widely deployed Linux kernels means that attackers with local access could leverage it to escalate privileges or destabilize systems, increasing the risk profile for European enterprises relying on Linux for secure network operations.

To mitigate CVE-2021-47082, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from trusted sources or Linux distributions. 2) Restrict local user access to systems running vulnerable kernels, limiting the ability of unprivileged users to invoke ioctl operations on TUN devices. 3) Employ mandatory access controls (e.g., SELinux, AppArmor) to tightly control permissions around network device management and ioctl interfaces. 4) Monitor kernel logs and audit systems for unusual ioctl calls or kernel crashes that may indicate exploitation attempts. 5) For environments using container or virtualized networking, ensure that container runtimes and orchestration platforms are updated to versions that include patched kernels or have mitigations in place. 6) Consider network segmentation to isolate critical Linux systems and reduce the attack surface. 7) Conduct regular vulnerability scanning and penetration testing focused on kernel-level vulnerabilities and local privilege escalation vectors. These steps go beyond generic advice by emphasizing access control, monitoring, and environment-specific hardening tailored to the nature of the vulnerability.