CVE-2025-21734 is a vulnerability identified in the Linux kernel's fastrpc driver, specifically related to the handling of non-registered buffers passed to a remote subsystem. The issue arises from an incorrect calculation of the page size during buffer copying. The current implementation calculates the page size without considering the offset within the buffer, leading to the possibility of passing an improper and out-of-bounds page size. This miscalculation can cause memory corruption issues, such as buffer overflows or access to unintended memory regions. The vulnerability stems from the failure to adjust the page start and page end addresses based on the offset, instead relying on absolute addresses. The fix involves recalculating these boundaries using the offset-adjusted address, ensuring that the copied buffer respects proper memory boundaries. While no known exploits are currently reported in the wild, the nature of the vulnerability suggests that it could be leveraged to cause memory corruption, potentially leading to denial of service (system crashes) or privilege escalation if exploited by a local attacker. The vulnerability affects specific versions of the Linux kernel identified by the commit hash 02b45b47fbe84e23699bb6bdc74d4c2780e282b4, indicating a narrow range of affected builds. No CVSS score has been assigned yet, and no patch links are provided in the data, but the issue has been publicly disclosed as of February 27, 2025.

For European organizations, the impact of CVE-2025-21734 could be significant, especially for those relying on Linux-based systems in critical infrastructure, telecommunications, cloud services, and embedded devices that utilize the fastrpc driver or similar kernel modules. Memory corruption vulnerabilities in the kernel can lead to system instability, crashes, or unauthorized privilege escalation, potentially allowing attackers to gain control over affected systems. This could disrupt business operations, compromise sensitive data, or facilitate lateral movement within networks. Given the Linux kernel's widespread use across servers, desktops, and IoT devices in Europe, organizations with unpatched systems may face increased risk of targeted attacks or exploitation attempts. The absence of known exploits in the wild currently reduces immediate risk, but the public disclosure may prompt attackers to develop exploits. Additionally, organizations in sectors with high regulatory requirements (e.g., finance, healthcare, energy) must consider the potential compliance implications of unmitigated kernel vulnerabilities.

European organizations should prioritize the following mitigation steps: 1) Identify and inventory all Linux systems using the affected kernel versions or the fastrpc driver, including embedded and IoT devices. 2) Apply the official kernel patches or updates that address the offset calculation issue as soon as they become available from trusted Linux distributions or kernel maintainers. 3) If immediate patching is not feasible, consider implementing temporary mitigations such as restricting access to vulnerable systems, enforcing strict user privilege separation, and monitoring for unusual system behavior indicative of memory corruption exploits. 4) Employ kernel hardening techniques like Kernel Address Space Layout Randomization (KASLR), and enable security modules such as SELinux or AppArmor to limit the impact of potential exploits. 5) Maintain up-to-date intrusion detection and prevention systems to detect anomalous activity related to kernel memory corruption attempts. 6) Engage in regular vulnerability scanning and penetration testing focused on kernel-level vulnerabilities to proactively identify exposure. 7) Educate system administrators and security teams about the specific nature of this vulnerability to ensure rapid response and remediation.