UBUNTU-CVE-2026-23428

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of share_conf in compound request smb2_get_ksmbd_tcon() reuses work->tcon in compound requests without validating tcon->t_state. ksmbd_tree_conn_lookup() checks t_state == TREE_CONNECTED on the initial lookup path, but the compound reuse path bypasses this check entirely. If a prior command in the compound (SMB2_TREE_DISCONNECT) sets t_state to TREE_DISCONNECTED and frees share_conf via ksmbd_share_config_put(), subsequent commands dereference the freed share_conf through work->tcon->share_conf. KASAN report: [ 4.144653] ================================================================== [ 4.145059] BUG: KASAN: slab-use-after-free in smb2_write+0xc74/0xe70 [ 4.145415] Read of size 4 at addr ffff88810430c194 by task kworker/1:1/44 [ 4.145772] [ 4.145867] CPU: 1 UID: 0 PID: 44 Comm: kworker/1:1 Not tainted 7.0.0-rc3+ #60 PREEMPTLAZY [ 4.145871] 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 [ 4.145875] Workqueue: ksmbd-io handle_ksmbd_work [ 4.145888] Call Trace: [ 4.145892] <TASK> [ 4.145894] dump_stack_lvl+0x64/0x80 [ 4.145910] print_report+0xce/0x660 [ 4.145919] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 4.145928] ? smb2_write+0xc74/0xe70 [ 4.145931] kasan_report+0xce/0x100 [ 4.145934] ? smb2_write+0xc74/0xe70 [ 4.145937] smb2_write+0xc74/0xe70 [ 4.145939] ? __pfx_smb2_write+0x10/0x10 [ 4.145942] ? _raw_spin_unlock+0xe/0x30 [ 4.145945] ? ksmbd_smb2_check_message+0xeb2/0x24c0 [ 4.145948] ? smb2_tree_disconnect+0x31c/0x480 [ 4.145951] handle_ksmbd_work+0x40f/0x1080 [ 4.145953] process_one_work+0x5fa/0xef0 [ 4.145962] ? assign_work+0x122/0x3e0 [ 4.145964] worker_thread+0x54b/0xf70 [ 4.145967] ? __pfx_worker_thread+0x10/0x10 [ 4.145970] kthread+0x346/0x470 [ 4.145976] ? recalc_sigpending+0x19b/0x230 [ 4.145980] ? __pfx_kthread+0x10/0x10 [ 4.145984] ret_from_fork+0x4fb/0x6c0 [ 4.145992] ? __pfx_ret_from_fork+0x10/0x10 [ 4.145995] ? __switch_to+0x36c/0xbe0 [ 4.145999] ? __pfx_kthread+0x10/0x10 [ 4.146003] ret_from_fork_asm+0x1a/0x30 [ 4.146013] </TASK> [ 4.146014] [ 4.149858] Allocated by task 44: [ 4.149953] kasan_save_stack+0x33/0x60 [ 4.150061] kasan_save_track+0x14/0x30 [ 4.150169] __kasan_kmalloc+0x8f/0xa0 [ 4.150274] ksmbd_share_config_get+0x1dd/0xdd0 [ 4.150401] ksmbd_tree_conn_connect+0x7e/0x600 [ 4.150529] smb2_tree_connect+0x2e6/0x1000 [ 4.150645] handle_ksmbd_work+0x40f/0x1080 [ 4.150761] process_one_work+0x5fa/0xef0 [ 4.150873] worker_thread+0x54b/0xf70 [ 4.150978] kthread+0x346/0x470 [ 4.151071] ret_from_fork+0x4fb/0x6c0 [ 4.151176] ret_from_fork_asm+0x1a/0x30 [ 4.151286] [ 4.151332] Freed by task 44: [ 4.151418] kasan_save_stack+0x33/0x60 [ 4.151526] kasan_save_track+0x14/0x30 [ 4.151634] kasan_save_free_info+0x3b/0x60 [ 4.151751] __kasan_slab_free+0x43/0x70 [ 4.151861] kfree+0x1ca/0x430 [ 4.151952] __ksmbd_tree_conn_disconnect+0xc8/0x190 [ 4.152088] smb2_tree_disconnect+0x1cd/0x480 [ 4.152211] handle_ksmbd_work+0x40f/0x1080 [ 4.152326] process_one_work+0x5fa/0xef0 [ 4.152438] worker_thread+0x54b/0xf70 [ 4.152545] kthread+0x346/0x470 [ 4.152638] ret_from_fork+0x4fb/0x6c0 [ 4.152743] ret_from_fork_asm+0x1a/0x30 [ 4.152853] [ 4.152900] The buggy address belongs to the object at ffff88810430c180 [ 4.152900] which belongs to the cache kmalloc-96 of size 96 [ 4.153226] The buggy address is located 20 bytes inside of [ 4.153226] freed 96-byte region [ffff88810430c180, ffff88810430c1e0) [ 4.153549] [ 4.153596] The buggy address belongs to the physical page: [ 4.153750] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88810430ce80 pfn:0x10430c [ 4.154000] flags: 0x ---truncated---

CVSS Metrics

• v4.0•HIGH•Score: 8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
• v3.1•CRITICAL•Score: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Systems

• ubuntu•linux

  all | all | all | all | < 5.15.0-185.195 | < 6.8.0-134.134 | < 6.17.0-40.40

• ubuntu•linux-allwinner-5.19

  all

• ubuntu•linux-aws

  all | all | all | all | < 5.15.0-1111.118 | < 6.8.0-1060.63 | < 6.17.0-1019.19

• ubuntu•linux-aws-5.0

  all

• ubuntu•linux-aws-5.11

  all

• ubuntu•linux-aws-5.13

  all

• ubuntu•linux-aws-5.15

  all | < 5.15.0-1111.118~20.04.1

• ubuntu•linux-aws-5.19

  all

• ubuntu•linux-aws-5.3

  all

• ubuntu•linux-aws-5.4

  all

• ubuntu•linux-aws-5.8

  all

• ubuntu•linux-aws-6.14

  all

• ubuntu•linux-aws-6.17

  all | < 6.17.0-1019.19~24.04.1

• ubuntu•linux-aws-6.2

  all

• ubuntu•linux-aws-6.5

  all

• ubuntu•linux-aws-6.8

  all | < 6.8.0-1060.63~22.04.1

• ubuntu•linux-aws-fips

  all | < 5.15.0-1111.118+fips1 | < 6.8.0-1060.63+fips1

• ubuntu•linux-aws-hwe

  all

• ubuntu•linux-azure

  all | all | all | < 5.15.0-1116.125 | all | all

• ubuntu•linux-azure-4.15

  all

• ubuntu•linux-azure-5.11

  all

• ubuntu•linux-azure-5.13

  all

• ubuntu•linux-azure-5.15

  all | < 5.15.0-1116.125~20.04.1

• ubuntu•linux-azure-5.19

  all

• ubuntu•linux-azure-5.3

  all

• ubuntu•linux-azure-5.4

  all

• ubuntu•linux-azure-5.8

  all

• ubuntu•linux-azure-6.11

  all

• ubuntu•linux-azure-6.14

  all

• ubuntu•linux-azure-6.17

  all

• ubuntu•linux-azure-6.2

  all

• ubuntu•linux-azure-6.5

  all

• ubuntu•linux-azure-6.8

  all

• ubuntu•linux-azure-edge

  all

• ubuntu•linux-azure-fde

  all | all | all | all

• ubuntu•linux-azure-fde-5.15

  all | < 5.15.0-1116.125~20.04.1

• ubuntu•linux-azure-fde-5.19

  all

• ubuntu•linux-azure-fde-6.14

  all

• ubuntu•linux-azure-fde-6.17

  all

• ubuntu•linux-azure-fde-6.2

  all

• ubuntu•linux-azure-fde-6.8

  all

• ubuntu•linux-azure-fips

  all | < 6.8.0-1062.69+fips1

• ubuntu•linux-azure-nvidia

  all

• ubuntu•linux-azure-nvidia-6.14

  all

• ubuntu•linux-bluefield

  all | < 5.15.0-1095.97 | all

• ubuntu•linux-fips

  all | < 5.15.0-185.195+fips1 | < 6.8.0-134.134+fips1

• ubuntu•linux-gcp

  all | all | all | all | all | < 5.15.0-1111.121 | < 6.8.0-1063.69 | < 6.17.0-1020.22

• ubuntu•linux-gcp-4.15

  all

• ubuntu•linux-gcp-5.11

  all

• ubuntu•linux-gcp-5.13

  all

Showing first 50 affected entries in server-rendered view.

References (28)

• https://ubuntu.com/security/CVE-2026-23428
• https://www.cve.org/CVERecord?id=CVE-2026-23428
• https://git.kernel.org/linus/c33615f995aee80657b9fdfbc4ee7f49c2bd733d
• https://git.kernel.org/stable/c/7f7468fd2a7554cea91b7d430335a3dbf01dcc09
• https://git.kernel.org/stable/c/806f13752652216db0c309392b4db3e64eeed4f2
• https://git.kernel.org/stable/c/a5929c2020ce54e1dcbd1078c0f30b8aaf73c105
• https://git.kernel.org/stable/c/c33615f995aee80657b9fdfbc4ee7f49c2bd733d
• https://git.kernel.org/stable/c/c742b46a153d3ff95ff0825ab1950c87b9e14470
• https://git.kernel.org/stable/c/eae0dc86f71e6f3294c0cd7ffc05039258d243af
• https://ubuntu.com/security/notices/USN-8490-1
• https://ubuntu.com/security/notices/USN-8491-1
• https://ubuntu.com/security/notices/USN-8492-1
• https://ubuntu.com/security/notices/USN-8493-1
• https://ubuntu.com/security/notices/USN-8492-2
• https://ubuntu.com/security/notices/USN-8497-1
• https://ubuntu.com/security/notices/USN-8498-1
• https://ubuntu.com/security/notices/USN-8499-1
• https://ubuntu.com/security/notices/USN-8493-2
• https://ubuntu.com/security/notices/USN-8508-1
• https://ubuntu.com/security/notices/USN-8492-3
• https://ubuntu.com/security/notices/USN-8490-2
• https://ubuntu.com/security/notices/USN-8492-4
• https://ubuntu.com/security/notices/USN-8492-5
• https://ubuntu.com/security/notices/USN-8527-1
• https://ubuntu.com/security/notices/USN-8528-1
• https://ubuntu.com/security/notices/USN-8545-1
• https://ubuntu.com/security/notices/USN-8546-1
• https://ubuntu.com/security/notices/USN-8547-1