Linux Kernel up to 7.1.7/7.2-rc5 KVM I/O APIC arch/x86/kvm/lapic.c __kvm_irq_delivery_to_apic_fast use after free

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.1.7/7.2-rc5. It has been rated as very critical. This affects the function __kvm_irq_delivery_to_apic_fast of the file arch/x86/kvm/lapic.c of the component KVM I/O APIC. The manipulation leads to use after free. This vulnerability is documented as CVE-2026-74517. The attack needs to be performed locally. There is not any exploit available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.1.7/7.2-rc5. It has been rated as very critical. This issue affects the function __kvm_irq_delivery_to_apic_fast of the file arch/x86/kvm/lapic.c of the component KVM I/O APIC. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Cancel delayed I/O APIC EOI handling before destroying vCPUs Cancel (and flush) the I/O APIC's delayed EOI handling work during the "pre VM destroy" phase, before vCPUs are destroyed, as processing the EOI broadcast will inject another IRQ if the line is asserted, i.e. will try to deliver an IRQ to the target vCPU(s). Canceling the work after vCPUs are destroyed leads to UAF if the delayed work is processed after vCPUs are destroyed. BUG: KASAN: slab-use-after-free in __kvm_irq_delivery_to_apic_fast+0x9bf/0xa20 arch/x86/kvm/lapic.c:1250 Read of size 8 at addr ffff8880499abea0 by task kworker/1:2/1218 CPU: 1 UID: 0 PID: 1218 Comm: kworker/1:2 Not tainted 7.1.0-rc7 #5 PREEMPT(lazy) Hardware name: QEMU Ubuntu 25.10 PC v2 (i440FX + PIIX, + 10.1 machine, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: events kvm_ioapic_eoi_inject_work Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 print_report+0x139/0x4ad mm/kasan/report.c:482 kasan_report+0xe4/0x1d0 mm/kasan/report.c:595 __kvm_irq_delivery_to_apic_fast+0x9bf/0xa20 arch/x86/kvm/lapic.c:1250 __kvm_irq_delivery_to_apic+0xd8/0xbf0 arch/x86/kvm/lapic.c:1345 kvm_irq_delivery_to_apic arch/x86/kvm/lapic.h:129 ioapic_service+0x308/0x590 arch/x86/kvm/ioapic.c:492 kvm_ioapic_eoi_inject_work+0x13c/0x190 arch/x86/kvm/ioapic.c:532 process_one_work+0xa59/0x19a0 kernel/workqueue.c:3314 process_scheduled_works kernel/workqueue.c:3397 worker_thread+0x5eb/0xe50 kernel/workqueue.c:3478 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd30 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> Note, the VM is unreachable once kvm_destroy_vm() starts, and scheduling new work via kvm_ioapic_send_eoi() can only be done via KVM_RUN, i.e. requires a live vCPU. Alternatively, KVM could simply destroy the I/O APIC during the "pre" phase of VM destruction, but that gets more than a bit sketchy as KVM expects the I/O APIC to exist if ioapic_in_kernel() is true, and nested virtualization in particular has a bad habit of touching VM-scope state during vCPU destruction. E.g. attempting to free the PIC during the pre phase would lead to a NULL pointer dereference in kvm_cpu_has_extint(), and it's not hard to imagine the I/O APIC having a similar flaw.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-74517 since 08/15/2026. The exploitation is known to be easy. An attack has to be approached locally. The exploitation needs additional levels of successful authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/15/2026).

Upgrading to version 7.1.8 or 7.2-rc6 eliminates this vulnerability. Applying the patch ed56a6b58222f9c1f4115a0bd2788dd6ed6022e2/9910e835580fef3bef53b70241dd00c4bffad693 is able to eliminate this problem.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.1.5
• 7.1.6
• 7.1.7
• 7.2-rc1
• 7.2-rc2
• 7.2-rc3
• 7.2-rc4
• 7.2-rc5

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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