CVE-2025-22024 is a vulnerability identified in the Linux kernel's NFS daemon (nfsd) subsystem, specifically related to the management of listener transports. The flaw arises when a root user executes the nfsdctl command to remove a particular listener from the list of previously added listeners while no active threads are running. The vulnerability is due to improper synchronization between two internal lists managing transport listeners: sv_permsocks and sp_xprts. When a listener is removed from sv_permsocks but not correspondingly from sp_xprts, a use-after-free condition occurs. This is evidenced by kernel warnings and trace logs indicating refcount_t addition on zero, which is a classic sign of reference counting errors leading to memory corruption. The root cause is that nfsd_nl_listener_set_doit() manipulates the sv_permsocks list to close the specified listener but neglects to update the sp_xprts list, causing stale pointers and potential memory corruption. The patch approach involves detecting when a listener removal is requested and then deleting all existing listener transports before re-creating all except the removed one, ensuring both lists remain consistent. This vulnerability affects Linux kernel versions containing the specified commit hashes and was publicly disclosed in April 2025. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a significant risk primarily to systems running Linux kernels with the affected nfsd versions, especially those utilizing NFS services for file sharing and network storage. Exploitation requires root privileges, which limits the attack vector but does not eliminate risk, as compromised or insider root access could trigger this flaw. The use-after-free condition can lead to kernel crashes (denial of service), potential escalation of privileges, or arbitrary code execution within the kernel context if exploited with sophisticated techniques. This could disrupt critical infrastructure, enterprise file servers, and cloud services relying on Linux-based NFS servers. Given the widespread use of Linux in European data centers, cloud providers, and enterprise environments, the vulnerability could impact availability and integrity of shared data. Additionally, the complexity of the flaw may allow attackers to evade detection, increasing the risk of persistent compromise. Organizations with high reliance on NFS for distributed storage or virtualization platforms (e.g., VMware environments running Linux guests) are particularly at risk.

1. Immediate application of the official Linux kernel patches that address this vulnerability is critical. Since the fix involves changes to the nfsd listener management code, upgrading to the latest stable kernel version containing the patch is recommended. 2. Restrict root access and enforce strict privilege management to prevent unauthorized execution of nfsdctl commands. 3. Implement kernel-level security modules (such as SELinux or AppArmor) with policies restricting modifications to NFS daemon configurations. 4. Monitor kernel logs for refcount warnings or unusual nfsdctl activity that may indicate exploitation attempts. 5. For environments where immediate patching is not feasible, consider disabling or restricting NFS services temporarily, especially on exposed or critical systems. 6. Conduct regular audits of NFS server configurations and listener states to detect inconsistencies. 7. Employ intrusion detection systems capable of monitoring kernel anomalies and unusual root-level command executions related to nfsd. 8. Ensure backups and disaster recovery plans are up to date to mitigate potential denial-of-service impacts.