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

IB/isert: delay the final Login Response until the session is registered

isert_put_login_tx() puts the final Login Response on the wire before
__transport_register_session(), which iscsi_post_login_handler() reaches
only after iscsi_target_do_login() returns. An initiator that issues a
SCSI command as soon as it sees that response can have it executed against
an se_session whose se_tpg is still NULL, and the ib-comp-wq worker oopses
on the NULL dereference.

Oops: general protection fault, probably for non-canonical address 0xdffffc000000000f: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000078-0x000000000000007f]
CPU: 0 UID: 0 PID: 178 Comm: kworker/0:1H Not tainted 7.2.0-rc5-V2CTL-gf5098b6bae76 #10 PREEMPT(lazy)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: ib-comp-wq ib_cq_poll_work
RIP: 0010:target_submit+0xbe/0x390
Code: fa 48 c1 ea 03 80 3c 02 00 0f 85 89 02 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 64 24 18 49 8d 7c 24 78 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 5a 02 00 00 48 8d 7b 78 4d 8b 6c 24 78 48 b8 00
RSP: 0018:ffff8881058cfa78 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff88810c78c6f0 RCX: ffffffff964bb363
RDX: 000000000000000f RSI: 00000000fffffe00 RDI: 0000000000000078
RBP: 1ffff11020b19f52 R08: 0000000000000001 R09: ffffed1020b19f52
R10: 0000000000000003 R11: ffff88810596c000 R12: 0000000000000000
R13: ffff88810c61b000 R14: ffff88810c6a3400 R15: ffff88810c61b044
FS: 0000000000000000(0000) GS:ffff8881822b2000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1f1b83c000 CR3: 000000006fe72001 CR4: 0000000000770ef0
PKRU: 55555554
Call Trace:
<TASK>
? __pfx__raw_spin_lock_bh+0x10/0x10
? __pfx_target_submit+0x10/0x10
? mutex_lock+0x81/0xe0
? __pfx_mutex_lock+0x10/0x10
? iscsit_execute_cmd+0x650/0x850
iscsit_sequence_cmd+0x186/0x3d0
iscsit_process_scsi_cmd+0x87/0x300
isert_recv_done+0x1002/0x2390
? __pfx_isert_recv_done+0x10/0x10
? rxe_poll_cq+0x253/0x3d0
? finish_task_switch.isra.0+0x1dc/0xa70
__ib_process_cq+0xe1/0x390
ib_cq_poll_work+0x46/0x150
process_one_work+0x633/0x1030
? assign_work+0x11d/0x370
worker_thread+0x45b/0xd10
? __pfx_worker_thread+0x10/0x10
? __pfx_worker_thread+0x10/0x10
kthread+0x2c6/0x3b0
? recalc_sigpending+0x15c/0x1e0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x36e/0x5a0
? __pfx_ret_from_fork+0x10/0x10
? __switch_to+0x572/0xdd0
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---

Delay the final Login Response instead. isert_get_rx_pdu() runs from
iscsi_target_rx_thread() after conn->rx_login_comp, completed by
iscsi_post_login_handler() after __transport_register_session(); iscsi-TCP
and cxgbit already take PDUs from that thread, isert alone does not. The
buffers are still posted first, so the initiator's first command does not
meet an empty receive queue and nothing depends on RNR flow control, and
the header and payload live in isert_conn, not in the struct iscsi_login
that iscsi_target_nego_release() frees first.

Over rxe, 400 login cycles per run, the oops appeared in 10 of 20
unpatched runs and in none of 20 runs with this patch. An
initiator that never waits is handled by the next patch.

Not tested: iWARP, discovery sessions over iSER, and real HCAs.
Published: 2026-09-17
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service via kernel crash
Action: Immediate Patch
AI Analysis

Impact

A null‑pointer dereference in the iSER target (isert) path is triggered when an initiator sends a SCSI command immediately after receiving a Login Response that is delivered before the session is fully registered. The kernel dereferences a NULL session pointer, causing a general protection fault and an oops that can lead to a kernel panic, thereby disrupting system availability.

Affected Systems

All Linux kernel releases that ship the isert (iSER) target module, which includes the default kernels of major distributions such as Ubuntu, Debian, Red Hat, and others. The vulnerability applies to any configuration where iSER is enabled; versions prior to the patch commit that delays the final Login Response are affected. Specific kernel versions are not listed, but the issue was demonstrated on a 7.2.x release.

Risk and Exploitability

The flaw is scored CVSS 7.5, indicating high severity. The EPSS score is under 1 %, reflecting a low likelihood of widespread exploitation at present. It is not listed in CISA’s KEV catalog. An attacker would need to act as an iSER initiator, establish a session, and issue SCSI commands as soon as the Login Response arrives. The attack is remote, does not provide execution privileges, but forces a kernel crash to deny service.

Generated by OpenCVE AI on September 20, 2026 at 02:00 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Update the kernel to a version that includes the patch that delays the final iSER Login Response until the session is registered.
  • If a kernel upgrade is not yet available, disable the isert module or unload it if the system does not require iSER target functionality.
  • Optionally block or throttle iSER traffic on the network to prevent initiators from sending commands immediately after login.

Generated by OpenCVE AI on September 20, 2026 at 02:00 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4817-1 linux-6.12 security update
Debian DSA Debian DSA DSA-6528-1 linux security update
History

Sun, 20 Sep 2026 02:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-476

Sat, 19 Sep 2026 16:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362
CWE-476

Sat, 19 Sep 2026 04:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362
CWE-476

Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Thu, 17 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: IB/isert: delay the final Login Response until the session is registered isert_put_login_tx() puts the final Login Response on the wire before __transport_register_session(), which iscsi_post_login_handler() reaches only after iscsi_target_do_login() returns. An initiator that issues a SCSI command as soon as it sees that response can have it executed against an se_session whose se_tpg is still NULL, and the ib-comp-wq worker oopses on the NULL dereference. Oops: general protection fault, probably for non-canonical address 0xdffffc000000000f: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000078-0x000000000000007f] CPU: 0 UID: 0 PID: 178 Comm: kworker/0:1H Not tainted 7.2.0-rc5-V2CTL-gf5098b6bae76 #10 PREEMPT(lazy) Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: ib-comp-wq ib_cq_poll_work RIP: 0010:target_submit+0xbe/0x390 Code: fa 48 c1 ea 03 80 3c 02 00 0f 85 89 02 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8b 64 24 18 49 8d 7c 24 78 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 5a 02 00 00 48 8d 7b 78 4d 8b 6c 24 78 48 b8 00 RSP: 0018:ffff8881058cfa78 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: ffff88810c78c6f0 RCX: ffffffff964bb363 RDX: 000000000000000f RSI: 00000000fffffe00 RDI: 0000000000000078 RBP: 1ffff11020b19f52 R08: 0000000000000001 R09: ffffed1020b19f52 R10: 0000000000000003 R11: ffff88810596c000 R12: 0000000000000000 R13: ffff88810c61b000 R14: ffff88810c6a3400 R15: ffff88810c61b044 FS: 0000000000000000(0000) GS:ffff8881822b2000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1f1b83c000 CR3: 000000006fe72001 CR4: 0000000000770ef0 PKRU: 55555554 Call Trace: <TASK> ? __pfx__raw_spin_lock_bh+0x10/0x10 ? __pfx_target_submit+0x10/0x10 ? mutex_lock+0x81/0xe0 ? __pfx_mutex_lock+0x10/0x10 ? iscsit_execute_cmd+0x650/0x850 iscsit_sequence_cmd+0x186/0x3d0 iscsit_process_scsi_cmd+0x87/0x300 isert_recv_done+0x1002/0x2390 ? __pfx_isert_recv_done+0x10/0x10 ? rxe_poll_cq+0x253/0x3d0 ? finish_task_switch.isra.0+0x1dc/0xa70 __ib_process_cq+0xe1/0x390 ib_cq_poll_work+0x46/0x150 process_one_work+0x633/0x1030 ? assign_work+0x11d/0x370 worker_thread+0x45b/0xd10 ? __pfx_worker_thread+0x10/0x10 ? __pfx_worker_thread+0x10/0x10 kthread+0x2c6/0x3b0 ? recalc_sigpending+0x15c/0x1e0 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x36e/0x5a0 ? __pfx_ret_from_fork+0x10/0x10 ? __switch_to+0x572/0xdd0 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1a/0x30 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- Delay the final Login Response instead. isert_get_rx_pdu() runs from iscsi_target_rx_thread() after conn->rx_login_comp, completed by iscsi_post_login_handler() after __transport_register_session(); iscsi-TCP and cxgbit already take PDUs from that thread, isert alone does not. The buffers are still posted first, so the initiator's first command does not meet an empty receive queue and nothing depends on RNR flow control, and the header and payload live in isert_conn, not in the struct iscsi_login that iscsi_target_nego_release() frees first. Over rxe, 400 login cycles per run, the oops appeared in 10 of 20 unpatched runs and in none of 20 runs with this patch. An initiator that never waits is handled by the next patch. Not tested: iWARP, discovery sessions over iSER, and real HCAs.
Title IB/isert: delay the final Login Response until the session is registered
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-18T17:54:24.543Z

Reserved: 2026-09-11T19:38:34.798Z

Link: CVE-2026-90294

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-17T17:17:26.693

Modified: 2026-09-18T18:17:52.480

Link: CVE-2026-90294

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-20T02:00:13Z

Weaknesses