CVE-2026-64141
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk37th percentile - higher than 37% of all known CVEs
Summary
In the Linux kernel's ksmbd filesystem, a null pointer dereference vulnerability exists in the compare_guid_key() function. During durable-handle session teardown, session_fd_check() sets the conn pointer in the opinfo structure to NULL but does not remove the opinfo from the lease list. When a new session is established with the same ClientGuid and an SMB2 CREATE request with a lease context is sent, find_same_lease_key() processes the stale opinfo, and compare_guid_key() attempts to read ClientGUID through a NULL conn pointer, causing a kernel panic.
Risk Assessment
An attacker can remotely trigger a kernel panic (denial of service) by sending a sequence of SMB2 requests: SESSION_SETUP, SESSION_LOGOFF, another SESSION_SETUP, and SMB2 CREATE with a lease context. Valid authentication and a share configured with 'durable handles = yes' are required.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit 70390501d194 or later). If an update is not possible, temporarily disable durable handles in the SMB share configuration.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix null pointer dereference in compare_guid_key() session_fd_check() walks the per-inode m_op_list during durable-handle session teardown and sets op->conn = NULL for every opinfo whose conn matched the closing session's connection. The matching opinfo, however, stays linked in its per-ClientGuid lease_table_list entry's lb->lease_list because destroy_lease_table() only runs on full TCP-connection teardown, not on SESSION_LOGOFF. If the same TCP connection then negotiates a fresh session with the same ClientGuid (ClientGuid is bound to NEGOTIATE, not the session, and is unchanged across LOGOFF + SETUP) and issues a SMB2 CREATE with a lease context on a different inode, find_same_lease_key() walks lb->lease_list, reaches the stale opinfo, and calls compare_guid_key(), which unconditionally dereferences opinfo->conn->ClientGUID. The conn pointer is NULL and the kernel panics. Reproducer requires only a successful SMB2 SESSION_SETUP and a share configured with 'durable handles = yes'. KASAN report on mainline 70390501d194: general protection fault, probably for non-canonical address 0xdffffc0000000069: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000348-0x000000000000034f] Workqueue: ksmbd-io handle_ksmbd_work RIP: 0010:bcmp+0x5b/0x230 Call Trace: compare_guid_key+0x4b/0xd0 find_same_lease_key+0x324/0x690 smb2_open+0x6aea/0x8e60 handle_ksmbd_work+0x796/0xee0 ... Faulting address 0x348 is the offset of ClientGUID within struct ksmbd_conn, confirming opinfo->conn was NULL. Read opinfo->conn once and bail out if it has been cleared by a concurrent session_fd_check(). A half-detached opinfo cannot be the owner of an active lease, so returning 0 is the correct match result.