CVE-2024-36031 is a critical vulnerability identified in the Linux kernel's key management subsystem, specifically related to the handling of key expiration during key instantiation. The flaw arises because the expiry time of a key is unconditionally overwritten during the instantiation process, defaulting the expiration time to TIME64_MAX, effectively making the key permanent. This behavior disrupts the intended expiration mechanism set by user-space applications, particularly impacting DNS resolution processes that rely on timely key expiration to manage DNS updates securely. The root cause is that the kernel fails to conditionally call the key_set_expiry function only when the pre-parser explicitly sets an expiry time, leading to an unconditional overwrite. This vulnerability is classified under CWE-324, which relates to the use of a key with an improper or missing expiration, potentially allowing unauthorized or unintended prolonged access. The CVSS v3.1 score of 9.8 (critical) reflects the high severity, with an attack vector that is network-based (AV:N), requiring no privileges (PR:N) and no user interaction (UI:N), and impacting confidentiality, integrity, and availability (C:H/I:H/A:H). Although no known exploits are currently reported in the wild, the vulnerability's nature and ease of exploitation make it a significant threat. The affected versions include multiple recent Linux kernel commits, indicating that this issue is present in actively maintained and widely deployed kernel versions. The fix involves restoring the conditional logic to ensure key_set_expiry is only invoked when a specific expiry is set by the pre-parser, thus preserving the intended expiration behavior and preventing keys from becoming permanent unintentionally.

For European organizations, the impact of CVE-2024-36031 can be substantial, especially for those relying heavily on Linux-based infrastructure for DNS services, authentication, and secure communications. The vulnerability undermines the key expiration mechanism, potentially allowing keys to remain valid indefinitely, which can lead to unauthorized access, persistent credential misuse, and disruption of DNS update processes. This can compromise the confidentiality and integrity of network communications and data, and also affect availability if DNS resolution is impaired. Critical sectors such as finance, telecommunications, government, and healthcare, which often use Linux servers for DNS and key management, are at heightened risk. The ability to exploit this vulnerability remotely without authentication or user interaction increases the threat landscape, potentially enabling attackers to establish persistent footholds or disrupt essential services. Given the widespread use of Linux in European data centers, cloud environments, and embedded systems, the vulnerability could have cascading effects on supply chains and service availability across multiple industries.

European organizations should prioritize patching affected Linux kernel versions immediately by applying the official fixes once available from trusted Linux distributions or kernel maintainers. In the interim, organizations can mitigate risk by auditing key management configurations to detect keys with unusually long or permanent expiration times and manually enforcing expiration policies where possible. Monitoring DNS update logs and key usage patterns can help identify anomalies indicative of exploitation attempts. Network segmentation and strict access controls around DNS and key management services can limit exposure. Additionally, organizations should implement robust logging and alerting mechanisms to detect unauthorized key usage or DNS update failures. Engaging with Linux vendor security advisories and subscribing to threat intelligence feeds will ensure timely awareness of exploit developments and patches. For critical systems, consider deploying kernel integrity monitoring tools and conducting regular security assessments focused on key management and DNS infrastructure.