CVE-2026-43232

Description

In the Linux kernel, the following vulnerability has been resolved: net: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets When the FarSync T-series card is being detached, the fst_card_info is deallocated in fst_remove_one(). However, the fst_tx_task or fst_int_task may still be running or pending, leading to use-after-free bugs when the already freed fst_card_info is accessed in fst_process_tx_work_q() or fst_process_int_work_q(). A typical race condition is depicted below: CPU 0 (cleanup) | CPU 1 (tasklet) | fst_start_xmit() fst_remove_one() | tasklet_schedule() unregister_hdlc_device()| | fst_process_tx_work_q() //handler kfree(card) //free | do_bottom_half_tx() | card-> //use The following KASAN trace was captured: ================================================================== BUG: KASAN: slab-use-after-free in do_bottom_half_tx+0xb88/0xd00 Read of size 4 at addr ffff88800aad101c by task ksoftirqd/3/32 ... Call Trace: <IRQ> dump_stack_lvl+0x55/0x70 print_report+0xcb/0x5d0 ? do_bottom_half_tx+0xb88/0xd00 kasan_report+0xb8/0xf0 ? do_bottom_half_tx+0xb88/0xd00 do_bottom_half_tx+0xb88/0xd00 ? _raw_spin_lock_irqsave+0x85/0xe0 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 ? __pfx___hrtimer_run_queues+0x10/0x10 fst_process_tx_work_q+0x67/0x90 tasklet_action_common+0x1fa/0x720 ? hrtimer_interrupt+0x31f/0x780 handle_softirqs+0x176/0x530 __irq_exit_rcu+0xab/0xe0 sysvec_apic_timer_interrupt+0x70/0x80 ... Allocated by task 41 on cpu 3 at 72.330843s: kasan_save_stack+0x24/0x50 kasan_save_track+0x17/0x60 __kasan_kmalloc+0x7f/0x90 fst_add_one+0x1a5/0x1cd0 local_pci_probe+0xdd/0x190 pci_device_probe+0x341/0x480 really_probe+0x1c6/0x6a0 __driver_probe_device+0x248/0x310 driver_probe_device+0x48/0x210 __device_attach_driver+0x160/0x320 bus_for_each_drv+0x101/0x190 __device_attach+0x198/0x3a0 device_initial_probe+0x78/0xa0 pci_bus_add_device+0x81/0xc0 pci_bus_add_devices+0x7e/0x190 enable_slot+0x9b9/0x1130 acpiphp_check_bridge.part.0+0x2e1/0x460 acpiphp_hotplug_notify+0x36c/0x3c0 acpi_device_hotplug+0x203/0xb10 acpi_hotplug_work_fn+0x59/0x80 ... Freed by task 41 on cpu 1 at 75.138639s: kasan_save_stack+0x24/0x50 kasan_save_track+0x17/0x60 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x43/0x70 kfree+0x135/0x410 fst_remove_one+0x2ca/0x540 pci_device_remove+0xa6/0x1d0 device_release_driver_internal+0x364/0x530 pci_stop_bus_device+0x105/0x150 pci_stop_and_remove_bus_device+0xd/0x20 disable_slot+0x116/0x260 acpiphp_disable_and_eject_slot+0x4b/0x190 acpiphp_hotplug_notify+0x230/0x3c0 acpi_device_hotplug+0x203/0xb10 acpi_hotplug_work_fn+0x59/0x80 ... The buggy address belongs to the object at ffff88800aad1000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 28 bytes inside of freed 1024-byte region The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xaad0 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x100000000000040(head|node=0|zone=1) page_type: f5(slab) raw: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000 raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 head: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000 head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 head: 0100000000000003 ffffea00002ab401 00000000ffffffff 00000000ffffffff head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88800aad0f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88800aad0f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88800aad1000: fa fb ---truncated---

CVSS Details

CVSS Score

8.8

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

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

Linux Kernel (主版本及稳定版)

Linux Kernel < 6.8 (需应用补丁)

PoC / Exploit Code

⚠ For Security Research Only

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

python

/*
 * PoC Concept for CVE-2026-43232
 * This code simulates the race condition between tasklet execution and device removal.
 * Note: Actual exploitation requires a specific environment with the vulnerable driver loaded.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>

struct fake_card {
    int data;
    // Simulating the fst_card_info structure
};

static struct fake_card *vulnerable_card;
static struct tasklet_struct tx_tasklet;

// Simulate the tasklet handler (fst_process_tx_work_q)
void tx_tasklet_handler(unsigned long data)
{
    struct fake_card *card = (struct fake_card *)data;
    
    // Introduce delay to increase window for race condition
    mdelay(100);
    
    // Access the card structure (Potential Use-After-Free)
    if (card) {
        printk(KERN_INFO "PoC: Accessing card data: %d\n", card->data);
    }
}

static int __init poc_init(void)
{
    vulnerable_card = kmalloc(sizeof(struct fake_card), GFP_KERNEL);
    if (!vulnerable_card)
        return -ENOMEM;
    
    vulnerable_card->data = 0x41414141;
    
    // Schedule the tasklet
    tasklet_init(&tx_tasklet, tx_tasklet_handler, (unsigned long)vulnerable_card);
    tasklet_schedule(&tx_tasklet);
    
    printk(KERN_INFO "PoC: Device initialized and tasklet scheduled.\n");
    
    // Simulate the removal race condition immediately
    // In the real vulnerability, fst_remove_one() does kfree(card) here
    // without checking if the tasklet is still running.
    printk(KERN_INFO "PoC: Simulating device removal (freeing memory)...\n");
    kfree(vulnerable_card);
    vulnerable_card = NULL;
    
    return 0;
}

static void __exit poc_exit(void)
{
    tasklet_kill(&tx_tasklet);
    printk(KERN_INFO "PoC: Exiting.\n");
}

module_init(poc_init);
module_exit(poc_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("PoC for CVE-2026-43232 Race Condition");

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43232
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43232
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43232/
[4] VulDB https://vuldb.com/cve/CVE-2026-43232
[5] https://git.kernel.org/stable/c/04edfdfdfcdefc02408ab670607261b0a0a9a02e
[6] https://git.kernel.org/stable/c/086131807d119238cd464e5b0845e48d938dfd79
[7] https://git.kernel.org/stable/c/200bdb8d367ca9b478f9c56ebe56411604d55c81
[8] https://git.kernel.org/stable/c/21d341fe514fd07e345ed264c9eee21cb2061ca2
[9] https://git.kernel.org/stable/c/337d7b4112a47984ee319171b75b73bab47e7924
[10] https://git.kernel.org/stable/c/ae894e47e1cd5a6bf8a0423d888c45df8b2b02dc
[11] https://git.kernel.org/stable/c/bae8a5d2e759da2e0cba33ab2080deee96a09373
[12] https://git.kernel.org/stable/c/cac048ebfbb92d91d719f74b59177cb70a7633b8

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43232", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-06T12:16:43.223", "lastModified": "2026-05-12T19:08:04.757", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets\n\nWhen the FarSync T-series card is being detached, the fst_card_info is\ndeallocated in fst_remove_one(). However, the fst_tx_task or fst_int_task\nmay still be running or pending, leading to use-after-free bugs when the\nalready freed fst_card_info is accessed in fst_process_tx_work_q() or\nfst_process_int_work_q().\n\nA typical race condition is depicted below:\n\nCPU 0 (cleanup) | CPU 1 (tasklet)\n | fst_start_xmit()\nfst_remove_one() | tasklet_schedule()\n unregister_hdlc_device()|\n | fst_process_tx_work_q() //handler\n kfree(card) //free | do_bottom_half_tx()\n | card-> //use\n\nThe following KASAN trace was captured:\n\n==================================================================\n BUG: KASAN: slab-use-after-free in do_bottom_half_tx+0xb88/0xd00\n Read of size 4 at addr ffff88800aad101c by task ksoftirqd/3/32\n ...\n Call Trace:\n <IRQ>\n dump_stack_lvl+0x55/0x70\n print_report+0xcb/0x5d0\n ? do_bottom_half_tx+0xb88/0xd00\n kasan_report+0xb8/0xf0\n ? do_bottom_half_tx+0xb88/0xd00\n do_bottom_half_tx+0xb88/0xd00\n ? _raw_spin_lock_irqsave+0x85/0xe0\n ? __pfx__raw_spin_lock_irqsave+0x10/0x10\n ? __pfx___hrtimer_run_queues+0x10/0x10\n fst_process_tx_work_q+0x67/0x90\n tasklet_action_common+0x1fa/0x720\n ? hrtimer_interrupt+0x31f/0x780\n handle_softirqs+0x176/0x530\n __irq_exit_rcu+0xab/0xe0\n sysvec_apic_timer_interrupt+0x70/0x80\n ...\n\n Allocated by task 41 on cpu 3 at 72.330843s:\n kasan_save_stack+0x24/0x50\n kasan_save_track+0x17/0x60\n __kasan_kmalloc+0x7f/0x90\n fst_add_one+0x1a5/0x1cd0\n local_pci_probe+0xdd/0x190\n pci_device_probe+0x341/0x480\n really_probe+0x1c6/0x6a0\n __driver_probe_device+0x248/0x310\n driver_probe_device+0x48/0x210\n __device_attach_driver+0x160/0x320\n bus_for_each_drv+0x101/0x190\n __device_attach+0x198/0x3a0\n device_initial_probe+0x78/0xa0\n pci_bus_add_device+0x81/0xc0\n pci_bus_add_devices+0x7e/0x190\n enable_slot+0x9b9/0x1130\n acpiphp_check_bridge.part.0+0x2e1/0x460\n acpiphp_hotplug_notify+0x36c/0x3c0\n acpi_device_hotplug+0x203/0xb10\n acpi_hotplug_work_fn+0x59/0x80\n ...\n\n Freed by task 41 on cpu 1 at 75.138639s:\n kasan_save_stack+0x24/0x50\n kasan_save_track+0x17/0x60\n kasan_save_free_info+0x3b/0x60\n __kasan_slab_free+0x43/0x70\n kfree+0x135/0x410\n fst_remove_one+0x2ca/0x540\n pci_device_remove+0xa6/0x1d0\n device_release_driver_internal+0x364/0x530\n pci_stop_bus_device+0x105/0x150\n pci_stop_and_remove_bus_device+0xd/0x20\n disable_slot+0x116/0x260\n acpiphp_disable_and_eject_slot+0x4b/0x190\n acpiphp_hotplug_notify+0x230/0x3c0\n acpi_device_hotplug+0x203/0xb10\n acpi_hotplug_work_fn+0x59/0x80\n ...\n\n The buggy address belongs to the object at ffff88800aad1000\n which belongs to the cache kmalloc-1k of size 1024\n The buggy address is located 28 bytes inside of\n freed 1024-byte region\n The buggy address belongs to the physical page:\n page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xaad0\n head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0\n flags: 0x100000000000040(head|node=0|zone=1)\n page_type: f5(slab)\n raw: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000\n raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000\n head: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000\n head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000\n head: 0100000000000003 ffffea00002ab401 00000000ffffffff 00000000ffffffff\n head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000\n page dumped because: kasan: bad access detected\n\n Memory state around the buggy address:\n ffff88800aad0f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc\n ffff88800aad0f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc\n >ffff88800aad1000: fa fb\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:R/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]} ... (truncated)