Executive brief
A vulnerability was identified in the Linux kernel's ksmbd component, which provides SMB file sharing services. The issue involves how the system identifies storage volumes, potentially allowing a local user to cause a system instability or denial of service. Patches have been released to ensure the system uses unique volume identifiers correctly.
Technical details
A vulnerability in the ksmbd (SMB server) implementation in the Linux kernel was resolved regarding the handling of FS_OBJECT_ID_INFORMATION. Previously, the code incorrectly used a user passkey or zeroed out the object ID instead of using unique volume identifiers. The fix modifies fs/smb/server/smb2pdu.c to use the superblock UUID (sb->s_uuid) as the primary identifier, falling back to the filesystem ID (f_fsid) from vfs_statfs() when a UUID is unavailable. This ensures unique and stable identification of filesystem objects. An attacker with local access could potentially exploit this logic error to cause a denial of service (system crash or hang).
Affected products
- Linux Linux Kernel 5.15 to 6.12.78, 6.13 to 6.18.20, 6.19 to 6.19.10, 7.0-rc1 to 7.0-rc4
Timeline
- 2026-04-06: disclosed
- 2026-04-06: advisory
- 2026-03-25: patched: Patches applied to various stable branches.