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Fencer Intel
high 8.8

CVE-2026-43232 json

net: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets

published 6mo ago modified 3mo ago also EUVD-2026-27795

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

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---

Patch / fix

  • Linux Linux 4.10, 4.15, 4.20, 5.5, 5.10.252, 5.15.202, 6.1, 6.1.165, 6.6.128, 6.12.75, 6.18.16, 6.19.6, 7.0
  • linux Debian 12 6.1.170-1
  • linux Debian 13 6.12.85-1
  • linux Debian 14 6.19.6-1

debian advisories DEBIAN-CVE-2026-43232

  • linux Ubuntu 22.04 LTS 5.15.0-186.196
  • linux Ubuntu 24.04 LTS 6.8.0-134.134
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1112.119
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1060.63
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1112.122
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1063.69
  • linux-gke Ubuntu 22.04 LTS 5.15.0-1108.114
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1058.64

ubuntu advisories UBUNTU-CVE-2026-43232

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-51.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.37.1
  • kernel-rt Linux Micro 6.2 6.12.0-160000.37.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.37.1

suse advisories SUSE-SU-2026:23244-1SUSE-SU-2026:23241-1SUSE-SU-2026:23194-1SUSE-SU-2026:23193-1SUSE-SU-2026:23237-1SUSE-SU-2026:23068-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.37.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.37.1

opensuse advisories openSUSE-SU-2026:21555-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-43232 updated

kernel: net: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.