Linux Kernel up to 6.1.159/6.6.119/6.12.63/6.18.2 KVM update_target_expiration denial of service

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5.0$0-$5k0.00

Summaryinfo

A vulnerability marked as critical has been reported in Linux Kernel up to 6.1.159/6.6.119/6.12.63/6.18.2. Affected is the function update_target_expiration of the component KVM. This manipulation causes denial of service. This vulnerability is registered as CVE-2025-71104. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.1.159/6.6.119/6.12.63/6.18.2. Affected by this vulnerability is the function update_target_expiration of the component KVM. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Fix VM hard lockup after prolonged inactivity with periodic HV timer When advancing the target expiration for the guest's APIC timer in periodic mode, set the expiration to "now" if the target expiration is in the past (similar to what is done in update_target_expiration()). Blindly adding the period to the previous target expiration can result in KVM generating a practically unbounded number of hrtimer IRQs due to programming an expired timer over and over. In extreme scenarios, e.g. if userspace pauses/suspends a VM for an extended duration, this can even cause hard lockups in the host. Currently, the bug only affects Intel CPUs when using the hypervisor timer (HV timer), a.k.a. the VMX preemption timer. Unlike the software timer, a.k.a. hrtimer, which KVM keeps running even on exits to userspace, the HV timer only runs while the guest is active. As a result, if the vCPU does not run for an extended duration, there will be a huge gap between the target expiration and the current time the vCPU resumes running. Because the target expiration is incremented by only one period on each timer expiration, this leads to a series of timer expirations occurring rapidly after the vCPU/VM resumes. More critically, when the vCPU first triggers a periodic HV timer expiration after resuming, advancing the expiration by only one period will result in a target expiration in the past. As a result, the delta may be calculated as a negative value. When the delta is converted into an absolute value (tscdeadline is an unsigned u64), the resulting value can overflow what the HV timer is capable of programming. I.e. the large value will exceed the VMX Preemption Timer's maximum bit width of cpu_preemption_timer_multi + 32, and thus cause KVM to switch from the HV timer to the software timer (hrtimers). After switching to the software timer, periodic timer expiration callbacks may be executed consecutively within a single clock interrupt handler, because hrtimers honors KVM's request for an expiration in the past and immediately re-invokes KVM's callback after reprogramming. And because the interrupt handler runs with IRQs disabled, restarting KVM's hrtimer over and over until the target expiration is advanced to "now" can result in a hard lockup. E.g. the following hard lockup was triggered in the host when running a Windows VM (only relevant because it used the APIC timer in periodic mode) after resuming the VM from a long suspend (in the host). NMI watchdog: Watchdog detected hard LOCKUP on cpu 45 ... RIP: 0010:advance_periodic_target_expiration+0x4d/0x80 [kvm] ... RSP: 0018:ff4f88f5d98d8ef0 EFLAGS: 00000046 RAX: fff0103f91be678e RBX: fff0103f91be678e RCX: 00843a7d9e127bcc RDX: 0000000000000002 RSI: 0052ca4003697505 RDI: ff440d5bfbdbd500 RBP: ff440d5956f99200 R08: ff2ff2a42deb6a84 R09: 000000000002a6c0 R10: 0122d794016332b3 R11: 0000000000000000 R12: ff440db1af39cfc0 R13: ff440db1af39cfc0 R14: ffffffffc0d4a560 R15: ff440db1af39d0f8 FS: 00007f04a6ffd700(0000) GS:ff440db1af380000(0000) knlGS:000000e38a3b8000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000d5651feff8 CR3: 000000684e038002 CR4: 0000000000773ee0 PKRU: 55555554 Call Trace: <IRQ> apic_timer_fn+0x31/0x50 [kvm] __hrtimer_run_queues+0x100/0x280 hrtimer_interrupt+0x100/0x210 ? ttwu_do_wakeup+0x19/0x160 smp_apic_timer_interrupt+0x6a/0x130 apic_timer_interrupt+0xf/0x20 </IRQ> Moreover, if the suspend duration of the virtual machine is not long enough to trigger a hard lockup in this scenario, since commit 98c25ead5eda ("KVM: VMX: Move preemption timer <=> hrtimer dance to common x86"), KVM will continue using the software timer until the guest reprograms the APIC timer in some way. Since the periodic timer does not require frequent APIC timer register programming, the guest may continue to use the software timer in ---truncated---

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2025-71104 since 01/13/2026. The exploitation appears to be difficult. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 284800 (Linux Distros Unpatched Vulnerability : CVE-2025-71104), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.1.160, 6.6.120, 6.12.64, 6.18.3 or 6.19-rc1 eliminates this vulnerability. Applying the patch 807dbe8f3862fa7c164155857550ce94b36a11b9/7b54ccef865e0aa62e4871d4ada2ba4b9dcb8bed/e746e51947053a02af2ea964593dc4887108d379/e23f46f1a971c73dad2fd63e1408696114ddebe2/18ab3fc8e880791aa9f7c000261320fc812b5465 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (284800) and CERT Bund (WID-SEC-2026-0119). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Debian Linux
  • Amazon Linux 2
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Open Source Linux Kernel

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.1
VulDB Meta Temp Score: 5.0

VulDB Base Score: 4.8
VulDB Temp Score: 4.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Denial of service
CWE: CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 284800
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2025-71104

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.1.160/6.6.120/6.12.64/6.18.3/6.19-rc1
Patch: 807dbe8f3862fa7c164155857550ce94b36a11b9/7b54ccef865e0aa62e4871d4ada2ba4b9dcb8bed/e746e51947053a02af2ea964593dc4887108d379/e23f46f1a971c73dad2fd63e1408696114ddebe2/18ab3fc8e880791aa9f7c000261320fc812b5465

Timelineinfo

01/13/2026 CVE reserved
01/14/2026 +1 days Advisory disclosed
01/14/2026 +0 days VulDB entry created
03/25/2026 +70 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-71104 (🔒)
GCVE (CVE): GCVE-0-2025-71104
GCVE (VulDB): GCVE-100-341065
CERT Bund: WID-SEC-2026-0119 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 01/14/2026 17:20
Updated: 03/25/2026 20:55
Changes: 01/14/2026 17:20 (59), 01/15/2026 21:30 (2), 01/16/2026 01:57 (7), 01/19/2026 18:09 (1), 03/09/2026 04:05 (1), 03/25/2026 20:55 (11)
Complete: 🔍
Cache ID: 216::103

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

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