The ksmbd service in the Linux kernel does not correctly populate the FileSysIdentifier field in the FS_POSIX_INFORMATION structure during SMB2 filesystem information queries. The eight‑byte field, which should carry the file system serial number obtained from statfs(), is left empty. When a client sends compound SMB2 requests, the response buffer can retain data from a previous reply; the empty field is then overwritten with leftover bytes, causing the kernel to transmit the server’s file system identifier to the client. This results in an information‑disclosure flaw that reveals low‑level system identifiers but does not provide any direct code execution or privilege escalation capability. The flaw is a classic example of CWE‑200: Information Exposure through Protocol Leak.

All Linux kernel builds that include the ksmbd component are potentially vulnerable, regardless of the kernel version, since the CVE data does not specify a limited range. The issue is confined to kernel images compiled with ksmbd enabled and with SMB2 support; users running a default distribution kernel with ksmbd active may therefore be exposed.

The public scanner metrics are missing a CVSS score and EPSS estimate, and the vulnerability is not listed in CISA’s KEV catalog, indicating a moderate publicly known risk. The likely attack vector is a network‑based attacker who can reach the SMB port and send crafted SMB2 compound requests. Exploitation requires only the ability to issue SMB commands; no authentication or privilege is required on the client side. Once triggered, the impact is limited to disclosure of the file system serial number, which may aid in reconnaissance or fingerprinting but does not directly compromise the system.