Linux Kernel ksmbd SMB server Vulnerability Rated 7.1 CVSS

Status: UPDATED  |  Advisory ID: CVE-2026-90174

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix slab-out-of-bounds read in ksmbd_alloc_user()

ksmbd_alloc_user() copies resp->hash_sz bytes out of the mountd IPC

login response with

user->passkey_sz = resp->hash_sz;

user->passkey = kmalloc(resp->hash_sz, KSMBD_DEFAULT_GFP);

if (user->passkey)

memcpy(user->passkey, resp->hash, resp->hash_sz);

resp->hash_sz is a __u16 supplied by the response, but resp->hash[] is

only KSMBD_REQ_MAX_HASH_SZ bytes. A malformed or malicious login

response can set hash_sz well beyond that (up to 65535), so the memcpy()

reads past the end of the response object. ipc_validate_msg() does not

bound hash_sz, so reject any response whose hash_sz exceeds the on-stack

hash[] buffer before allocating and copying.

[ 2030.238706] BUG: KASAN: slab-out-of-bounds in ksmbd_alloc_user+0x278/0x680

[ 2030.240549] Read of size 65535 at addr ffff888121bb6680 by task kworker/4:1/18611

[ 2030.242296]

[ 2030.242710] CPU: 4 UID: 0 PID: 18611 Comm: kworker/4:1 Not tainted 7.1.0-next-20260623-virtme #96 PREEMPT(lazy)

[ 2030.242732] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014

[ 2030.242743] Workqueue: ksmbd-io handle_ksmbd_work

[ 2030.242763] Call Trace:

[ 2030.242769] <TASK>

[ 2030.242776] dump_stack_lvl+0xa2/0xd0

[ 2030.242794] print_address_description+0x77/0x200

[ 2030.242815] ? ksmbd_alloc_user+0x278/0x680

[ 2030.242831] print_report+0x58/0x70

[ 2030.242848] kasan_report+0x117/0x150

[ 2030.242869] ? ksmbd_alloc_user+0x278/0x680

[ 2030.242888] kasan_check_range+0x3c7/0x3f0

[ 2030.242908] ? ksmbd_alloc_user+0x278/0x680

[ 2030.242925] __asan_memcpy+0x29/0x70

[ 2030.242942] ksmbd_alloc_user+0x278/0x680

[ 2030.242960] ksmbd_login_user+0xc3/0x120

[ 2030.242978] ntlm_authenticate+0x5e6/0x1b00

[ 2030.243017] ? __pfx_ntlm_authenticate+0x10/0x10

[ 2030.243035] ? ksmbd_session_lookup+0x188/0x1d0

[ 2030.243054] ? __pfx_ksmbd_session_lookup+0x10/0x10

[ 2030.243090] ? __sanitizer_cov_trace_switch+0x7b/0x140

[ 2030.243108] smb2_sess_setup+0x1e4a/0x27b0

[ 2030.243126] ? copy_from_kernel_nofault+0x199/0x300

[ 2030.243156] ? __pfx_smb2_sess_setup+0x10/0x10

[ 2030.243173] ? get_smb2_cmd_val+0xe3/0x1c0

[ 2030.243208] handle_ksmbd_work+0x954/0x1280

[ 2030.243230] ? __pfx_handle_ksmbd_work+0x10/0x10

[ 2030.243249] ? process_scheduled_works+0xa07/0x1490

[ 2030.243270] ? process_scheduled_works+0xa07/0x1490

[ 2030.243291] process_scheduled_works+0xa70/0x1490

[ 2030.243320] ? __pfx_process_scheduled_works+0x10/0x10

[ 2030.243340] ? do_raw_spin_lock+0x130/0x300

[ 2030.243358] ? lock_is_held_type+0x7b/0x110

[ 2030.243388] worker_thread+0x932/0xe20

[ 2030.243415] kthread+0x38a/0x470

[ 2030.243431] ? __pfx_worker_thread+0x10/0x10

[ 2030.243451] ? __pfx_kthread+0x10/0x10

[ 2030.243467] ret_from_fork+0x484/0x910

[ 2030.243485] ? __pfx_ret_from_fork+0x10/0x10

[ 2030.243501] ? __switch_to+0xc77/0x12c0

[ 2030.243523] ? __pfx_kthread+0x10/0x10

[ 2030.243540] ret_from_fork_asm+0x1a/0x30

[ 2030.243564] </TASK>

[ 2030.243570]

[ 2030.290164] Allocated by task 19279:

[ 2030.290911] kasan_save_track+0x3e/0x80

[ 2030.292179] __kasan_kmalloc+0x72/0x90

[ 2030.293217] __kvmalloc_node_noprof+0x3ff/0x6b0

[ 2030.294467] handle_generic_event+0x59b/0x750

[ 2030.295345] genl_family_rcv_msg_doit+0x238/0x340

[ 2030.296553] genl_rcv_msg+0x606/0x7b0

[ 2030.297129] netlink_rcv_skb+0x22b/0x4a0

[ 2030.298500] genl_rcv+0x2d/0x40

[ 2030.299273] netlink_unicast+0x7ba/0x930

[ 2030.300019] netlink_sendmsg+0x8c3/0xb00

[ 2030.301073] __sock_sendmsg+0xec/0x140

[ 2030.301579] __sys_sendto+0x357/0x470

[ 2030.302255] __x64_sys_sendto+0xe3/0x100

[ 2030.303425] do_syscall_64+0x135/0x460

[ 2030.304763] entry_SYSCALL_64_after_hwframe+0x77/0x7f

[ 2030.305594]

[ 2030.305819] The buggy address belongs to the object at ffff888121bb6640

[ 2030.305819] which belongs to the cache kmalloc-192 of size 192

[ 2030.309595] The buggy address

---truncated--- (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References