CVE-2024-26835 is a vulnerability identified in the Linux kernel's netfilter subsystem, specifically within the nf_tables component responsible for packet filtering and firewall functionality. The issue arises when the kernel attempts to register hooks during nf_tables operations. Under conditions of memory pressure, the hook registration can fail, but the system does not correctly set the 'dormant' flag on the table. This results in a table being marked as active despite having no registered hooks. Consequently, when the table or its base chain is deleted, nf_tables attempts to unregister hooks that were never successfully registered, leading to kernel warnings (warn splats) and potential instability. Although this vulnerability does not directly indicate a remote code execution or privilege escalation vector, the improper state management of nf_tables could cause kernel warnings and potentially impact system stability or availability. The vulnerability affects multiple Linux kernel versions as indicated by the affected commit hashes, and it was publicly disclosed on April 17, 2024. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The root cause is a failure to reset the dormant flag on hook registration failure, which is a logic flaw in the kernel's netfilter hook management under resource constraints.

For European organizations, the impact of CVE-2024-26835 primarily concerns system stability and availability rather than direct compromise of confidentiality or integrity. Systems running vulnerable Linux kernel versions with nf_tables enabled may experience kernel warnings or instability under memory pressure conditions, potentially leading to service disruptions. This could affect critical infrastructure, cloud services, and enterprise environments relying on Linux-based firewalls or packet filtering. Although no active exploitation is known, the vulnerability could be leveraged in denial-of-service scenarios if an attacker induces memory pressure or triggers hook registration failures, causing kernel instability or crashes. This is particularly relevant for organizations with high availability requirements such as financial institutions, telecommunications providers, and public sector entities. The vulnerability does not appear to allow privilege escalation or remote code execution, so the confidentiality impact is limited. However, the availability impact could be significant in environments where nf_tables is heavily used and memory resources are constrained.

To mitigate CVE-2024-26835, European organizations should prioritize updating their Linux kernels to versions where this vulnerability is patched. Since the issue stems from improper flag management during hook registration failure, applying the official kernel patches or upgrading to a fixed kernel release is the most effective mitigation. Organizations should also monitor system logs for kernel warnings related to nf_tables and netfilter hooks, which could indicate attempts to trigger this condition. Additionally, system administrators should ensure adequate memory resources are available to reduce the likelihood of memory pressure conditions that cause hook registration failures. For environments with strict uptime requirements, consider implementing kernel live patching solutions where available to apply fixes without downtime. Network security teams should review firewall and packet filtering configurations to ensure they are resilient and consider fallback mechanisms if nf_tables hooks fail. Finally, maintain vigilance for any emerging exploit reports or advisories related to this vulnerability.