CVE-2024-26642 addresses a vulnerability within the Linux kernel's netfilter subsystem, specifically in the nf_tables component. Netfilter is a framework used for packet filtering, network address translation (NAT), and other packet mangling operations in the Linux kernel. The nf_tables module is a modern replacement for older iptables infrastructure, providing more flexible and efficient packet filtering capabilities. The vulnerability pertains to the handling of anonymous sets with the timeout flag. Anonymous sets in nf_tables are collections of elements used for matching packets, and the timeout flag allows elements to expire after a certain period. According to the vulnerability description, anonymous sets are never intended to be used with the timeout flag from userspace. The Linux kernel previously did not enforce this restriction, potentially allowing malformed or malicious netfilter rules to be created that misuse anonymous sets with timeouts. This could lead to undefined behavior or security issues such as memory corruption or denial of service. The patch enforces a rejection of anonymous sets with timeout flags except for the NFT_SET_EVAL exception, which is maintained to ensure compatibility with legacy meters. This fix prevents userspace from creating potentially dangerous netfilter configurations that could exploit this flaw. There are no known exploits in the wild at the time of publication, and the vulnerability was reserved in February 2024 and published in March 2024. No CVSS score has been assigned yet, and no detailed CWE classification is provided. The affected versions are identified by a specific commit hash, indicating that this vulnerability affects certain recent Linux kernel versions prior to the patch.

For European organizations, this vulnerability could have significant implications, especially for those relying heavily on Linux-based infrastructure for networking, firewalls, and security appliances. Since netfilter and nf_tables are widely used for packet filtering and firewalling on Linux servers, routers, and embedded devices, exploitation could allow attackers to disrupt network traffic, cause denial of service, or potentially escalate privileges if the kernel memory is corrupted. This could impact critical services, including web servers, VPN gateways, and cloud infrastructure that use Linux extensively. The lack of known exploits suggests the threat is currently theoretical, but the potential for misuse in complex network environments remains. Organizations in sectors such as finance, telecommunications, government, and critical infrastructure, which often deploy Linux-based network security solutions, could be particularly affected. The impact on confidentiality and integrity is moderate to high if attackers can manipulate firewall rules or cause kernel instability. Availability could also be affected due to potential crashes or resource exhaustion. Given the kernel-level nature of the vulnerability, successful exploitation could have broad system-wide consequences.

European organizations should prioritize applying the official Linux kernel patches that enforce the restriction on anonymous sets with timeout flags in nf_tables. Kernel updates should be tested and deployed promptly in all affected environments. Network administrators should audit existing netfilter rulesets to ensure no anonymous sets with timeout flags are in use, especially in custom or legacy configurations. Monitoring tools should be enhanced to detect unusual netfilter rule changes or attempts to create anonymous sets with timeouts. Additionally, organizations should implement strict access controls to limit who can modify netfilter configurations, as exploitation requires privileged access to configure firewall rules. Employing kernel hardening techniques and using security modules like SELinux or AppArmor can further reduce the risk of exploitation. For environments using legacy meters relying on NFT_SET_EVAL, ensure that only trusted users can manage these configurations. Regular vulnerability scanning and compliance checks should include verification of kernel versions and patch status related to this CVE. Finally, maintain awareness of any emerging exploit reports or advisories related to this vulnerability.