CVE-2026-90172 smb: smbdirect: destroy QP before mem pools on accept failure
A use-after-free vulnerability in the Linux kernel's SMB Direct module allows a local attacker to cause a system crash via a NULL pointer dereference.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90172?
CVE-2026-90172 is a high-severity use after free vulnerability in Linux, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
smb: smbdirect: destroy QP before mem pools on accept failure
On the rdma_accept_failed error path of smbdirect_accept_connect_request(), the receive io posted just above is owned by the QP (recv_io is set to NULL after a successful post). The error path fell through to smbdirect_connection_destroy_mem_pools() before smbdirect_connection_destroy_qp(), so the mem pools and the recv_io slab cache were destroyed while that recv_io was still outstanding on the QP.
The drain in smbdirect_connection_destroy_qp() (ib_drain_qp()) is what runs the recv completion that returns the recv_io to the free list, so destroying the pools first leaves the object outstanding at kmem_cache_destroy() time ("Slab cache still has objects") and later frees it into an already-destroyed mempool (mempool_free_bulk NULL-pointer dereference).
Give rdma_accept_failed its own teardown that drains the QP first, then destroys the mem pools, and returns. The remaining labels (post_recv_io_failed onward) run before the recv_io was ever posted, so they keep the mem-pools-then-qp order.
The outstanding recv_io at kmem_cache_destroy() time:
[ 3487.344647] ============================================================================= [ 3487.349942] BUG smbdirect_recv_io_cache_ffff88811ba99000 (Not tainted): Objects remaining on __kmem_cache_shutdown() [ 3487.356078] ----------------------------------------------------------------------------- [ 3487.356078] [ 3487.356738] Object 0xffff8881511c3440 @offset=13376 [ 3487.358464] Allocated in mempool_alloc_noprof+0x18c/0x290 age=1194 cpu=6 pid=22254 [ 3487.361197] mempool_alloc_noprof+0x18c/0x290 [ 3487.361542] smbdirect_connection_create_mem_pools+0x405/0x780 [ 3487.361972] smbdirect_accept_connect_request+0x5a8/0x1b80 [ 3487.362359] smbdirect_listen_rdma_event_handler+0x1579/0x1b90 [ 3487.362779] cma_cm_event_handler+0x9c/0x230 [ 3487.363096] cma_ib_req_handler+0x2682/0x45d0 [ 3487.363414] cm_process_work+0x56/0x3d0 [ 3487.363676] cm_work_handler+0x8a0e/0xd000 [ 3487.367496] process_scheduled_works+0xa07/0x13a0 [ 3487.367859] worker_thread+0x7c9/0xc80 [ 3487.368148] kthread+0x341/0x430 [ 3487.368407] ret_from_fork+0x3a8/0x7a0 [ 3487.368704] ret_from_fork_asm+0x1a/0x30 [ 3487.370307] Slab 0xffffea0005447000 objects=19 used=1 fp=0xffff8881511c0040 flags=0x100000000000240(workingset|head|node=0|zone=2) [ 3487.372840] ------------[ cut here ]------------ [ 3487.373195] WARNING: mm/slub.c:1244 at __slab_err+0x1a/0x30, CPU#6: kworker/6:84/22254 [ 3487.373759] Modules linked in: [ 3487.373993] CPU: 6 UID: 0 PID: 22254 Comm: kworker/6:84 Tainted: G B 7.1.0-next-20260623+ #88 PREEMPT(lazy) [ 3487.374778] Tainted: [B]=BAD_PAGE [ 3487.377830] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014 [ 3487.378515] Workqueue: ib_cm cm_work_handler [ 3487.378820] RIP: 0010:__slab_err+0x1a/0x30 [ 3487.379129] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 e8 36 00 00 00 bf 05 00 00 00 be 01 00 00 00 e8 f7 75 45 00 90 <0f> 0b 90 c3 cc cc cc cc cc 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 [ 3487.383255] RSP: 0018:ffff888220fc7050 EFLAGS: 00010093 [ 3487.383643] RAX: ffffffff8168e60a RBX: ffff88810955e640 RCX: ffff88821c381d80 [ 3487.384158] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff870fa080 [ 3487.384662] RBP: ffff888220fc7068 R08: ffffffff870fa087 R09: 1ffffffff0e1f410 [ 3487.385192] R10: dffffc0000000000 R11: fffffbfff0e1f411 R12: ffffea0005447210 [ 3487.385674] R13: ffffea0005447000 R14: ffff888220fc7068 R15: ffff88812a8ab300 [ 3487.388932] FS: 0000000000000000(0000) GS:ffff888427e76000(0000) knlGS:0000000000000000 [ 3487.389529] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 3487.389934] CR2: 00007ffcf2d84fd8 CR3: 0000000111d64006 CR4: 0000000000f72ef0 [ 3487.390440] PKRU: 55555554 [ 3487.390641] Call Trace: [ 3487.390826] <TASK> [ 3 ---truncated---
Which versions are affected by CVE-2026-90172?
How do I fix CVE-2026-90172?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-90172 being exploited?
There is no known exploitation of CVE-2026-90172 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90172, GHSA-pqj5-pgr6-pmv4, UBUNTU-CVE-2026-90172.