CVE-2025-21760 is a high-severity vulnerability in the Linux kernel related to the Neighbor Discovery Protocol (NDP) implementation, specifically within the ndisc_send_skb() function. The flaw arises because ndisc_send_skb() can be invoked without holding the RTNL (rtnetlink) lock or RCU (Read-Copy-Update) protection, which are synchronization mechanisms critical for safe concurrent access to kernel data structures. Without proper locking, the function may access freed memory, leading to a Use-After-Free (UAF) condition (CWE-416). This vulnerability could allow an attacker with limited privileges (local access with low privileges) to cause memory corruption, potentially leading to arbitrary code execution, privilege escalation, or denial of service. The fix involves acquiring the rcu_read_lock() earlier in the function to ensure safe access to dev_net_rcu() and prevent the UAF scenario. The vulnerability affects specific Linux kernel versions identified by commit hashes, indicating it impacts recent kernel builds. The CVSS v3.1 score is 7.8 (high), reflecting high impact on confidentiality, integrity, and availability, with low attack complexity and requiring low privileges but no user interaction. No known exploits are currently reported in the wild, but the nature of the vulnerability and its kernel-level impact make it a significant threat once weaponized.

For European organizations, this vulnerability poses a substantial risk, especially for enterprises relying heavily on Linux-based infrastructure such as servers, cloud environments, and network appliances. Exploitation could lead to unauthorized privilege escalation, allowing attackers to gain root access, compromise sensitive data, disrupt critical services, or establish persistent footholds. This is particularly concerning for sectors like finance, telecommunications, government, and critical infrastructure operators in Europe, where Linux is widely deployed. The potential for denial of service or system crashes could also impact availability of essential services. Given the kernel-level nature of the flaw, remediation delays could expose organizations to targeted attacks or lateral movement within networks. The absence of known exploits currently provides a window for proactive patching and mitigation.

1. Immediate application of official Linux kernel patches that address CVE-2025-21760 is critical. Organizations should track kernel updates from their Linux distribution vendors and deploy them promptly. 2. For environments where immediate patching is challenging, consider isolating vulnerable systems or restricting local user access to minimize exploitation risk. 3. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), Control Flow Integrity (CFI), and seccomp filters to reduce exploitation likelihood. 4. Monitor system logs and kernel messages for unusual behavior indicative of exploitation attempts, such as unexpected crashes or memory corruption signs. 5. Use security tools capable of detecting anomalous kernel activity or privilege escalation attempts. 6. Conduct thorough testing of kernel updates in staging environments to ensure stability before production deployment, minimizing operational disruption. 7. Educate system administrators about the vulnerability specifics and the importance of timely patching and monitoring.