CVE-2025-21997 is a vulnerability identified in the Linux kernel's XDP (eXpress Data Path) subsystem, specifically within the xsk (AF_XDP socket) implementation. The flaw arises due to an integer overflow in the function xp_create_and_assign_umem(). This function handles the creation and assignment of user memory (umem) for zero-copy packet processing. The vulnerability is caused because the variables 'i' and 'pool->chunk_size' are both 32-bit unsigned integers (u32). When their product is calculated, it can overflow (wrap around) before being cast to a 64-bit unsigned integer (u64). This overflow leads to incorrect memory size calculations, resulting in two different XDP buffers potentially pointing to the same physical memory area. Such a condition can cause memory corruption, data races, or unintended data leakage between buffers. The issue was discovered by InfoTeCS on behalf of the Linux Verification Center using static analysis tools (SVACE). While no known exploits are currently reported in the wild, the vulnerability affects Linux kernel versions identified by the commit hashes provided, indicating it is present in recent kernel builds before the patch. The lack of a CVSS score suggests the vulnerability is newly disclosed and not yet fully assessed. However, the technical nature of the flaw indicates a serious risk in environments using AF_XDP sockets for high-performance packet processing, such as network appliances, firewalls, or load balancers running on Linux. Attackers with the ability to manipulate XDP buffers could exploit this flaw to cause memory corruption or potentially escalate privileges or cause denial of service.

For European organizations, the impact of CVE-2025-21997 can be significant, especially for those relying on Linux-based network infrastructure or edge computing devices that utilize XDP for packet processing acceleration. The vulnerability could lead to memory corruption, resulting in system instability, crashes, or data leakage between network buffers. This can degrade the availability and integrity of critical network services, including firewalls, intrusion detection systems, and load balancers. Confidentiality could also be compromised if sensitive data is inadvertently shared between buffers. Given the widespread use of Linux in European data centers, telecom infrastructure, and cloud environments, exploitation could disrupt business operations, impact service delivery, and expose sensitive information. Although exploitation requires specific conditions (access to AF_XDP sockets), insider threats or attackers who have gained initial footholds could leverage this vulnerability to escalate privileges or move laterally within networks. The absence of known exploits currently reduces immediate risk, but the vulnerability's nature demands prompt attention to avoid future exploitation as attackers develop techniques.

European organizations should prioritize patching affected Linux kernel versions as soon as vendor updates become available to address CVE-2025-21997. Until patches are applied, organizations should audit and restrict access to AF_XDP socket interfaces, limiting usage to trusted processes and users only. Network administrators should monitor kernel logs and system behavior for anomalies related to XDP buffer handling. Deploying runtime security tools that detect memory corruption or unusual socket activity can provide early warning signs. For environments where patching is delayed, consider disabling or limiting XDP and AF_XDP socket usage if feasible, especially on critical systems. Additionally, organizations should review their network device configurations and container orchestration platforms to ensure that unprivileged containers or applications do not have unnecessary access to raw packet processing features. Implementing strict kernel module loading policies and using security modules like SELinux or AppArmor to confine network-related processes can further reduce exploitation risk. Finally, maintain up-to-date incident response plans to quickly address any signs of exploitation related to this vulnerability.