CVE-2024-50106 is a high-severity use-after-free vulnerability in the Linux kernel's NFS server daemon (nfsd), specifically affecting the handling of state IDs (stid) related to NFSv4 delegations. The vulnerability arises from a race condition between the laundromat thread, which manages expired delegation revocations, and a client thread processing the free_stateid operation. When a delegation expires, the laundromat marks the delegation's stid as revoked and places it on a reaper list before unlocking the state lock. Concurrently, a free_stateid thread may remove the stid from the reaper list and free its memory without proper synchronization. This leads to a use-after-free scenario when a new open operation on the same file attempts to access the freed stid, causing kernel memory corruption and triggering Kernel Address Sanitizer (KASAN) warnings. The root cause is the improper coordination between the laundromat and free_stateid operations, resulting in the laundromat skipping the revoke_delegation() call and failing to release the file lease lock. The patch introduces two new stid status values to coordinate these operations, ensuring that once a stid is marked revoked, it is not prematurely removed or freed. It also adjusts the handling of delegation returns to correctly return nfserr_deleg_revoked instead of nfserr_bad_stateid, preventing indefinite retention of revoked delegations on the cl_revoked list. This vulnerability is tracked under CWE-416 (Use After Free) and has a CVSS 3.1 score of 7.8, reflecting its high impact on confidentiality, integrity, and availability. Exploitation requires local privileges with low complexity and no user interaction, but it can lead to kernel crashes or potentially privilege escalation due to memory corruption.

For European organizations, this vulnerability poses significant risks, especially for enterprises and service providers relying on Linux-based NFS servers for file sharing and storage. The use-after-free flaw can cause kernel crashes leading to denial of service (DoS) conditions, disrupting critical business operations and data availability. More critically, memory corruption vulnerabilities in the kernel can be leveraged by attackers with local access to escalate privileges, potentially compromising entire systems and sensitive data. Organizations in sectors such as finance, healthcare, government, and telecommunications, which often use NFS for shared storage, are particularly at risk. The vulnerability's exploitation could lead to unauthorized data access, data integrity violations, and prolonged service outages. Given the widespread deployment of Linux servers across Europe, the impact could be broad, affecting both private enterprises and public sector infrastructure.

European organizations should prioritize applying the official Linux kernel patches that address CVE-2024-50106 as soon as they become available. Until patches are deployed, organizations should: 1) Restrict local access to NFS servers to trusted users only, minimizing the risk of exploitation by unprivileged users. 2) Implement strict access controls and monitoring on NFS server processes to detect anomalous behavior indicative of exploitation attempts. 3) Consider temporarily disabling NFSv4 delegation features if feasible, as the vulnerability specifically involves delegation state handling. 4) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar memory corruption issues proactively. 5) Maintain up-to-date intrusion detection and prevention systems capable of identifying exploitation patterns targeting NFS services. 6) Conduct thorough audits of NFS server configurations and usage to ensure minimal exposure. These measures, combined with timely patching, will reduce the risk and impact of this vulnerability.