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Linux Kernel EUVDEUVD-2026-27795

| CVE-2026-43232 HIGH
Use After Free (CWE-416)
2026-05-06 Linux GHSA-84hg-9fjm-pcr7
Information Disclosure Linux Memory Corruption Use After Free Red Hat Suse
8.8
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
SUSE
HIGH
qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
May 08, 2026 - 13:40 vuln.today
CVSS changed
May 08, 2026 - 13:22 NVD
8.8 (HIGH)
Patch available
May 06, 2026 - 13:32 EUVD
CVE Published
May 06, 2026 - 11:28 nvd
HIGH 8.8

DescriptionCVE.org

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---

AnalysisAI

Use-after-free in Linux kernel farsync driver allows remote code execution when FarSync T-series WAN cards are detached while tasklets remain active. The vulnerability occurs when fst_tx_task or fst_int_task continue executing after fst_card_info is freed in fst_remove_one(), causing the kernel to access deallocated memory. Despite the CVSS 8.8 score with network vector, the EPSS score is extremely low (0.02%, 7th percentile), suggesting minimal real-world exploitation likelihood. No active exploitation confirmed (not in CISA KEV). Patches available across multiple stable kernel versions (5.10.252, 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16, 6.19.6, 7.0).

Technical ContextAI

The FarSync T-series WAN card driver uses Linux kernel tasklets (fst_tx_task and fst_int_task) for deferred interrupt processing. Tasklets are a bottom-half interrupt handling mechanism that execute asynchronously in softirq context. The vulnerability stems from improper synchronization during driver cleanup: when pci_device_remove calls fst_remove_one(), the fst_card_info structure is freed via kfree() without ensuring pending tasklets are cancelled. If fst_start_xmit() schedules a tasklet just before device removal, the tasklet handler (fst_process_tx_work_q() calling do_bottom_half_tx()) executes after the card structure is freed, dereferencing invalid memory. This is a classic use-after-free race condition where object lifetime management fails across concurrent execution contexts. The KASAN trace shows the freed object being accessed 28 bytes into a 1024-byte kmalloc-1k allocation, confirming slab-use-after-free detection. CPE data indicates broad exposure across multiple Linux kernel versions from commit 2f623aaf9f31 onward until patched versions.

RemediationAI

Upgrade to patched Linux kernel versions: 5.10.252, 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16, 6.19.6, or 7.0 depending on your kernel branch. Patches available from git.kernel.org stable tree (commits listed in affected_products section). For systems that cannot immediately upgrade, the compensating control is to blacklist the farsync kernel module if FarSync T-series hardware is not actively required - add 'blacklist farsync' to /etc/modprobe.d/blacklist.conf and rebuild initramfs, then reboot. This prevents module loading entirely, eliminating the vulnerable code path. Trade-off: FarSync WAN cards become non-functional until patched kernel is deployed. Alternatively, disable PCI hot-plug for systems with FarSync cards to prevent the device removal race condition - edit ACPI hot-plug settings or use 'pci=noacpi' boot parameter, though this affects all hot-plug capability system-wide and may interfere with virtualization platforms. The module blacklist approach is cleanest for most environments not using this legacy WAN hardware. Verify farsync module is loaded with 'lsmod | grep farsync' before applying mitigations.

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Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed

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EUVD-2026-27795 vulnerability details – vuln.today
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