CVE-2026-43232
Awaiting Analysis Awaiting Analysis - Queue
Use-After-Free in FarSync T-Series Linux Kernel Driver

Publication date: 2026-05-06

Last updated on: 2026-05-06

Assigner: kernel.org

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 Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-05-06
Last Modified
2026-05-06
Generated
2026-05-07
AI Q&A
2026-05-06
EPSS Evaluated
N/A
NVD
CVE-2026-43232
EUVD
EUVD-2026-27795
Affected Vendors & Products
Currently, no data is known.
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a use-after-free bug in the Linux kernel's FarSync T-series card driver. When the card is detached, the associated data structure (fst_card_info) is freed, but certain tasks (fst_tx_task or fst_int_task) may still be running or scheduled to run. These tasks can then access the already freed memory, leading to use-after-free errors.

The issue arises due to a race condition between the cleanup process that frees the card information and the tasklets that process transmit or interrupt work queues. This can cause the kernel to access invalid memory, potentially leading to crashes or undefined behavior.


How can this vulnerability impact me? :

This vulnerability can cause system instability or crashes due to the kernel accessing freed memory. It may lead to kernel panics or other unpredictable behavior, which can disrupt normal system operations.

In environments using the affected FarSync T-series card, this bug could result in denial of service or potentially be exploited to execute arbitrary code within the kernel context, depending on the attacker's capabilities.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability involves use-after-free bugs in the Linux kernel related to the FarSync T-series card when it is detached. Detection can be done by monitoring kernel logs for KASAN (Kernel Address Sanitizer) reports indicating slab-use-after-free errors in functions like do_bottom_half_tx or fst_process_tx_work_q.

To detect this vulnerability on your system, you can check the kernel logs for KASAN error messages using commands such as:

  • dmesg | grep -i kasan
  • journalctl -k | grep -i kasan
  • grep -r 'slab-use-after-free' /var/log/

These commands help identify if the kernel has logged any use-after-free bugs related to the FarSync driver. Additionally, monitoring for system crashes or instability when detaching the FarSync T-series card may also indicate the presence of this issue.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability is caused by use-after-free bugs in the FarSync T-series card driver in the Linux kernel. Immediate mitigation steps include:

  • Avoid detaching or removing the FarSync T-series card until a patched kernel version is applied.
  • Update the Linux kernel to a version where this vulnerability has been fixed, as indicated by the patch to fix use-after-free bugs in fst_remove_one() and related functions.
  • If updating the kernel is not immediately possible, consider disabling the FarSync T-series card or its driver to prevent triggering the bug.

Monitoring kernel logs for KASAN errors can also help identify if the vulnerability is being triggered, allowing for timely response.


Ask Our AI Assistant
Need more information? Ask your question to get an AI reply (Powered by our expertise)
0/70
EPSS Chart