CVE-2022-48827 is a vulnerability in the Linux kernel's Network File System daemon (NFSD) related to handling READ requests near the maximum file offset (OFFSET_MAX). The issue arises from a prior commit that aligned read buffer sizes on the client side, causing a read request near the maximum 64-bit file offset (0x7fffffffffffffff) to overflow the server's internal loff_t type, which is used to represent file offsets. Specifically, when a client attempts to read from an offset close to this maximum value, the server's offset calculation overflows, resulting in an invalid argument error (EINVAL) being returned to the client. However, the Linux NFS client does not properly handle the NFS error code ERR_INVAL, which is permitted by NFS specifications for READ operations. Instead of gracefully handling this error, the client indefinitely retries the request, potentially causing resource exhaustion or denial of service on the server or client side. The fix involves changing the server behavior to allow out-of-range READ requests to succeed by returning a short read result and setting the EOF flag, preventing the client from retrying. This approach aligns with behavior observed in Solaris NFS servers. The root cause is the improper conversion of 64-bit offset values (u64) from the NFS protocol into the internal loff_t type, which requires careful handling to avoid overflow and ensure correct validation against maximum file size limits. This vulnerability affects Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and similar builds. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations relying on Linux-based NFS servers or clients, this vulnerability could lead to denial of service conditions. Specifically, a malicious or misconfigured NFS client could send crafted READ requests near the maximum file offset, causing the server to return errors that the client mishandles by retrying indefinitely. This behavior can lead to resource exhaustion on both client and server, potentially degrading service availability. Critical infrastructure, cloud providers, and enterprises using NFS for file sharing and storage in Europe could experience disruptions. Additionally, since NFS is widely used in enterprise and data center environments, this vulnerability could be exploited to cause performance degradation or outages in shared storage environments. Although no direct data confidentiality or integrity compromise is indicated, the availability impact could be significant, especially in environments with high NFS traffic or where automated systems rely on stable NFS mounts. The lack of proper error handling also indicates a robustness issue in the Linux NFS client implementation, which could affect operational stability.

European organizations should promptly update their Linux kernels to versions that include the patch for CVE-2022-48827. Since the vulnerability is related to the Linux kernel's NFS client and server code, applying official kernel updates from trusted Linux distributions is the most effective mitigation. In environments where immediate patching is not feasible, administrators should consider limiting NFS client access to trusted hosts and monitoring for unusual NFS READ request patterns near the maximum offset values. Network-level controls such as firewall rules or NFS protocol filtering could help mitigate exploitation attempts. Additionally, auditing and logging NFS errors and client retries can help detect potential exploitation attempts. Organizations should also review their NFS client implementations and configurations to ensure they handle server error codes correctly and do not retry indefinitely on ERR_INVAL responses. Engaging with Linux distribution vendors for backported patches and security advisories is recommended. Finally, testing NFS client and server behavior in controlled environments after patching is advised to confirm the fix and prevent regressions.