CVE-2024-27065 is a vulnerability identified in the Linux kernel's netfilter subsystem, specifically within the nf_tables component. Netfilter is a framework used for packet filtering, network address translation (NAT), and other packet mangling operations within the Linux kernel. The nf_tables module is a modern replacement for older iptables, ip6tables, arptables, and ebtables frameworks, providing a more flexible and efficient way to manage firewall rules. The vulnerability relates to the handling of internal table flags during updates. The issue arises because the kernel did not properly compare internal table flags when updating nf_tables configurations. This flaw could cause the system to skip the transaction if the table update does not modify the flags, potentially leading to inconsistent or unintended firewall states. This behavior could be exploited by an attacker with the ability to modify nf_tables configurations to bypass certain firewall rules or cause denial of service by disrupting expected firewall behavior. The vulnerability was reserved in February 2024 and published in May 2024, with no known exploits in the wild reported so far. The affected versions are various Linux kernel commits identified by their hashes, indicating that multiple recent kernel versions were impacted before the fix was applied. No CVSS score has been assigned yet, and no detailed CWE classification is provided. The fix involves restoring the skipping of transactions only when appropriate, ensuring that updates to nf_tables are correctly processed even if internal flags remain unchanged.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with the affected nf_tables versions, which is common in servers, network appliances, and embedded devices. The potential impact includes unauthorized modification or bypass of firewall rules, which could allow attackers to circumvent network security controls, leading to unauthorized access, data exfiltration, or lateral movement within networks. Additionally, inconsistent firewall states could cause denial of service conditions by disrupting legitimate traffic flows or firewall operations. Organizations relying on Linux-based firewalls or network filtering appliances could see degraded security postures or operational disruptions. Given that nf_tables is widely used in modern Linux distributions, the vulnerability could affect a broad range of sectors including finance, healthcare, government, and critical infrastructure in Europe. The absence of known exploits reduces immediate risk, but the vulnerability's presence in a core kernel component means that once exploit techniques are developed, the impact could be significant. The complexity of the vulnerability suggests that exploitation requires local privileges or administrative access to modify firewall rules, which somewhat limits the attack surface but does not eliminate risk, especially in multi-tenant or cloud environments.

European organizations should prioritize updating their Linux kernels to versions where this vulnerability is patched. Since the issue lies in the nf_tables subsystem, kernel updates from trusted Linux distribution vendors (such as Debian, Ubuntu, Red Hat, SUSE, and others) should be applied promptly. Network administrators should audit firewall configurations and monitor for unusual changes or failures in firewall rule application. Implementing strict access controls and monitoring on systems that manage firewall rules can reduce the risk of unauthorized modifications. Additionally, organizations should consider deploying host-based intrusion detection systems (HIDS) to detect anomalous behavior related to firewall rule changes. For environments using containerization or virtualization, ensure that host kernels are updated, as containerized applications rely on the host kernel's networking stack. Finally, maintain robust logging and alerting for netfilter/nf_tables events to quickly identify potential exploitation attempts or misconfigurations.