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 Details

CVSS Score

9.8

Severity

CRITICAL

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel (ksmbd) < 6.8-rc1 (Patches apply to stable branches)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#!/usr/bin/env python3
"""
PoC for CVE-2026-23428: ksmbd Use-After-Free
This script demonstrates the logic to trigger the vulnerability by sending
a compound request containing SMB2_TREE_DISCONNECT followed by SMB2_WRITE.
"""

import socket
import struct

def send_exploit(target_ip):
    """
    Sends a malicious compound request to the target ksmbd server.
    """
    # Setup socket connection to SMB port (445)
    try:
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.connect((target_ip, 445))
        print(f"[+] Connected to {target_ip}:445")

        # Note: In a real scenario, full SMB negotiation and session setup
        # would be performed here. This PoC focuses on the payload structure.

        # Construct Compound Request:
        # 1. SMB2_TREE_DISCONNECT (Frees share_conf)
        # 2. SMB2_WRITE (Attempts to use freed share_conf)
        # The vulnerability occurs because the second command reuses the
        # work->tcon pointer without checking if it was disconnected by the first.
        
        payload = b""
        # SMB2 Header for TREE_DISCONNECT
        # ... (Header bytes) ...
        
        # SMB2 Header for WRITE (Chained)
        # ... (Header bytes) ...

        s.send(payload)
        print("[+] Malicious compound request sent.")
        print("[+] Check target kernel logs for KASAN use-after-free detection.")
        
        s.close()
    except Exception as e:
        print(f"[-] Error: {e}")

if __name__ == "__main__":
    # Replace with actual target IP
    TARGET = "192.168.1.10"
    send_exploit(TARGET)

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23428
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23428
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23428/
[4] VulDB https://vuldb.com/cve/CVE-2026-23428
[5] https://git.kernel.org/stable/c/7f7468fd2a7554cea91b7d430335a3dbf01dcc09
[6] https://git.kernel.org/stable/c/806f13752652216db0c309392b4db3e64eeed4f2
[7] https://git.kernel.org/stable/c/a5929c2020ce54e1dcbd1078c0f30b8aaf73c105
[8] https://git.kernel.org/stable/c/c33615f995aee80657b9fdfbc4ee7f49c2bd733d
[9] https://git.kernel.org/stable/c/c742b46a153d3ff95ff0825ab1950c87b9e14470
[10] https://git.kernel.org/stable/c/d08417981155883068b7260d9500ca306a03edac
[11] https://git.kernel.org/stable/c/eae0dc86f71e6f3294c0cd7ffc05039258d243af

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23428", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-03T16:16:23.993", "lastModified": "2026-04-27T14:16:32.177", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free of share_conf in compound request\n\nsmb2_get_ksmbd_tcon() reuses work->tcon in compound requests without\nvalidating tcon->t_state. ksmbd_tree_conn_lookup() checks t_state ==\nTREE_CONNECTED on the initial lookup path, but the compound reuse path\nbypasses this check entirely.\n\nIf a prior command in the compound (SMB2_TREE_DISCONNECT) sets t_state\nto TREE_DISCONNECTED and frees share_conf via ksmbd_share_config_put(),\nsubsequent commands dereference the freed share_conf through\nwork->tcon->share_conf.\n\nKASAN report:\n\n[ 4.144653] ==================================================================\n[ 4.145059] BUG: KASAN: slab-use-after-free in smb2_write+0xc74/0xe70\n[ 4.145415] Read of size 4 at addr ffff88810430c194 by task kworker/1:1/44\n[ 4.145772]\n[ 4.145867] CPU: 1 UID: 0 PID: 44 Comm: kworker/1:1 Not tainted 7.0.0-rc3+ #60 PREEMPTLAZY\n[ 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\n[ 4.145875] Workqueue: ksmbd-io handle_ksmbd_work\n[ 4.145888] Call Trace:\n[ 4.145892] <TASK>\n[ 4.145894] dump_stack_lvl+0x64/0x80\n[ 4.145910] print_report+0xce/0x660\n[ 4.145919] ? __pfx__raw_spin_lock_irqsave+0x10/0x10\n[ 4.145928] ? smb2_write+0xc74/0xe70\n[ 4.145931] kasan_report+0xce/0x100\n[ 4.145934] ? smb2_write+0xc74/0xe70\n[ 4.145937] smb2_write+0xc74/0xe70\n[ 4.145939] ? __pfx_smb2_write+0x10/0x10\n[ 4.145942] ? _raw_spin_unlock+0xe/0x30\n[ 4.145945] ? ksmbd_smb2_check_message+0xeb2/0x24c0\n[ 4.145948] ? smb2_tree_disconnect+0x31c/0x480\n[ 4.145951] handle_ksmbd_work+0x40f/0x1080\n[ 4.145953] process_one_work+0x5fa/0xef0\n[ 4.145962] ? assign_work+0x122/0x3e0\n[ 4.145964] worker_thread+0x54b/0xf70\n[ 4.145967] ? __pfx_worker_thread+0x10/0x10\n[ 4.145970] kthread+0x346/0x470\n[ 4.145976] ? recalc_sigpending+0x19b/0x230\n[ 4.145980] ? __pfx_kthread+0x10/0x10\n[ 4.145984] ret_from_fork+0x4fb/0x6c0\n[ 4.145992] ? __pfx_ret_from_fork+0x10/0x10\n[ 4.145995] ? __switch_to+0x36c/0xbe0\n[ 4.145999] ? __pfx_kthread+0x10/0x10\n[ 4.146003] ret_from_fork_asm+0x1a/0x30\n[ 4.146013] </TASK>\n[ 4.146014]\n[ 4.149858] Allocated by task 44:\n[ 4.149953] kasan_save_stack+0x33/0x60\n[ 4.150061] kasan_save_track+0x14/0x30\n[ 4.150169] __kasan_kmalloc+0x8f/0xa0\n[ 4.150274] ksmbd_share_config_get+0x1dd/0xdd0\n[ 4.150401] ksmbd_tree_conn_connect+0x7e/0x600\n[ 4.150529] smb2_tree_connect+0x2e6/0x1000\n[ 4.150645] handle_ksmbd_work+0x40f/0x1080\n[ 4.150761] process_one_work+0x5fa/0xef0\n[ 4.150873] worker_thread+0x54b/0xf70\n[ 4.150978] kthread+0x346/0x470\n[ 4.151071] ret_from_fork+0x4fb/0x6c0\n[ 4.151176] ret_from_fork_asm+0x1a/0x30\n[ 4.151286]\n[ 4.151332] Freed by task 44:\n[ 4.151418] kasan_save_stack+0x33/0x60\n[ 4.151526] kasan_save_track+0x14/0x30\n[ 4.151634] kasan_save_free_info+0x3b/0x60\n[ 4.151751] __kasan_slab_free+0x43/0x70\n[ 4.151861] kfree+0x1ca/0x430\n[ 4.151952] __ksmbd_tree_conn_disconnect+0xc8/0x190\n[ 4.152088] smb2_tree_disconnect+0x1cd/0x480\n[ 4.152211] handle_ksmbd_work+0x40f/0x1080\n[ 4.152326] process_one_work+0x5fa/0xef0\n[ 4.152438] worker_thread+0x54b/0xf70\n[ 4.152545] kthread+0x346/0x470\n[ 4.152638] ret_from_fork+0x4fb/0x6c0\n[ 4.152743] ret_from_fork_asm+0x1a/0x30\n[ 4.152853]\n[ 4.152900] The buggy address belongs to the object at ffff88810430c180\n[ 4.152900] which belongs to the cache kmalloc-96 of size 96\n[ 4.153226] The buggy address is located 20 bytes inside of\n[ 4.153226] freed 96-byte region [ffff88810430c180, ffff88810430c1e0)\n[ 4.153549]\n[ 4.153596] The buggy address belongs to the physical page:\n[ 4.153750] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88810430ce80 pfn:0x10430c\n[ 4.154000] flags: 0x\n---truncated---"}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}, {"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H ... (truncated)