CVE-2024-26782 is a vulnerability in the Linux kernel's Multipath TCP (MPTCP) implementation, specifically related to the handling of socket dismantling. When an MPTCP server accepts an incoming connection, it clones its listener socket. However, the pointer to the 'inet_opt' structure for the new socket is not properly duplicated and instead shares the same memory reference as the original socket. This leads to a double-free condition during socket teardown, as both sockets attempt to free the same memory region. The vulnerability manifests as a kernel memory corruption issue, detected by Kernel Address Sanitizer (KASAN) as a double-free in the inet_sock_destruct function. The detailed kernel stack trace shows that the double-free occurs during socket destruction and involves multiple kernel functions related to socket lifecycle management and TCP cleanup. The affected Linux kernel versions include those identified by the commit hash cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be, indicating a specific patch or code state. This flaw can cause kernel crashes (BUG splats), leading to denial of service (DoS) conditions. Although no known exploits are currently reported in the wild, the vulnerability is critical because it involves kernel memory corruption, which could potentially be leveraged for privilege escalation or arbitrary code execution if combined with other vulnerabilities or attack vectors. The issue does not require user interaction but does require the system to be running MPTCP with server socket cloning, which is common in modern Linux kernels used in servers and network appliances. The vulnerability was publicly disclosed on April 4, 2024, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a significant risk primarily to servers and network infrastructure running Linux kernels with MPTCP enabled. Many European enterprises, cloud providers, and telecom operators rely on Linux-based systems for critical services, including web hosting, telecommunications, and cloud infrastructure. Exploitation could lead to kernel crashes causing service outages, impacting availability of critical services. In worst-case scenarios, attackers might chain this vulnerability with others to gain elevated privileges or execute arbitrary code at the kernel level, compromising confidentiality and integrity of sensitive data. Given the widespread use of Linux in European data centers and telecom networks, the vulnerability could disrupt business operations, especially in sectors like finance, healthcare, and government where uptime and data integrity are paramount. Additionally, the vulnerability could be exploited in multi-tenant cloud environments, affecting multiple customers. The lack of known exploits currently reduces immediate risk, but the potential for future exploitation necessitates prompt mitigation.

European organizations should immediately assess their Linux kernel versions and configurations to determine exposure to this vulnerability. Specific mitigation steps include: 1) Applying the official Linux kernel patches that fix the double-free issue in the MPTCP socket handling code as soon as they become available from trusted sources or vendor distributions. 2) Temporarily disabling MPTCP functionality on affected systems if patching is not immediately feasible, especially on servers exposed to untrusted networks. 3) Implementing strict network segmentation and firewall rules to limit exposure of MPTCP-enabled services to trusted clients only. 4) Monitoring kernel logs and system behavior for signs of crashes or anomalies related to socket handling. 5) Employing kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar memory corruption issues proactively. 6) Coordinating with Linux distribution vendors for timely updates and advisories. 7) For cloud providers, isolating workloads and applying micro-segmentation to reduce blast radius in case of exploitation. These measures go beyond generic advice by focusing on MPTCP-specific configurations and kernel patch management.