CVE-2025-22056 is a vulnerability identified in the Linux kernel's netfilter subsystem, specifically within the nft_tunnel module that handles Geneve (Generic Network Virtualization Encapsulation) options parsing. The flaw arises due to improper pointer arithmetic and type conversion when processing multiple NFTA_TUNNEL_KEY_OPTS_GENEVE attributes. The parsing logic is supposed to sequentially and compactly place each geneve_opt structure by advancing the pointer in units of bytes (char *). However, the existing implementation incorrectly performs type conversion before pointer addition, leading to a heap out-of-bounds write. This memory corruption is confirmed by Kernel Address Sanitizer (KASAN) logs showing slab-out-of-bounds writes during nft_tunnel_obj_init execution. The vulnerability allows an attacker with the ability to send crafted netlink messages to the kernel's nftables interface to trigger out-of-bounds writes on the heap. This can cause kernel crashes (denial of service) or potentially enable privilege escalation or arbitrary code execution within the kernel context if exploited further. The issue affects Linux kernel versions prior to the patch that corrects the pointer arithmetic and type conversion in the parsing and dumping code of Geneve options. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability requires local or network-level access to send malicious netlink messages, but no user interaction beyond that is needed. The flaw impacts the integrity and availability of the system by corrupting kernel memory and causing instability or compromise.

For European organizations, this vulnerability poses a significant risk, especially for those relying heavily on Linux-based infrastructure, including servers, network appliances, and cloud environments. The netfilter subsystem is widely used for firewalling and network packet filtering, so exploitation could disrupt critical network security functions. An attacker exploiting this vulnerability could cause kernel panics leading to denial of service, impacting availability of services. More critically, if combined with other exploits, it could lead to privilege escalation or arbitrary code execution at the kernel level, compromising confidentiality and integrity of sensitive data. Organizations running containerized workloads or virtualized environments using Geneve tunnels for network overlay could be particularly exposed. The lack of a public exploit currently reduces immediate risk, but the vulnerability's presence in the Linux kernel—a core component in many European government, financial, and industrial systems—makes timely patching essential to prevent potential targeted attacks. The complexity of the vulnerability means that skilled attackers with access to internal networks or compromised hosts could leverage it to escalate privileges or disrupt operations.

European organizations should prioritize updating Linux kernels to versions where this vulnerability is patched. Since the issue lies in the netfilter nft_tunnel module, kernel upgrades from trusted sources or vendor-provided security patches should be applied promptly. Network administrators should audit and restrict access to netlink interfaces, limiting which users or processes can send nftables netlink messages, reducing the attack surface. Employing kernel hardening features such as Kernel Address Sanitizer (KASAN) in testing environments can help detect similar issues early. For environments using Geneve tunnels, monitoring and logging netlink communications for anomalous or malformed messages can provide early warning signs. Additionally, organizations should implement strict network segmentation and access controls to prevent unauthorized lateral movement that could lead to exploitation. Regular vulnerability scanning and penetration testing focusing on kernel-level vulnerabilities and privilege escalation paths are recommended. Finally, maintain robust incident response plans to quickly address any kernel-level compromises.