CVE-2026-43315

MEDIUM EPSS 3.0%
Published May 8, 20261mo ago · Modified Jun 17, 20261w ago
5.5 CVSS 3.1
Medium
Find Similar
Published May 8, 2026 1mo ago
Last Modified Jun 17, 2026 1w ago

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: nSVM: Remove a user-triggerable WARN on nested_svm_load_cr3() succeeding Drop the WARN in svm_set_nested_state() on nested_svm_load_cr3() failing as it is trivially easy to trigger from userspace by modifying CPUID after loading CR3. E.g. modifying the state restoration selftest like so: --- tools/testing/selftests/kvm/x86/state_test.c +++ tools/testing/selftests/kvm/x86/state_test.c @@ -280,7 +280,16 @@ int main(int argc, char *argv[]) /* Restore state in a new VM. */ vcpu = vm_recreate_with_one_vcpu(vm); - vcpu_load_state(vcpu, state); + + if (stage == 4) { + state->sregs.cr3 = BIT(44); + vcpu_load_state(vcpu, state); + + vcpu_set_cpuid_property(vcpu, X86_PROPERTY_MAX_PHY_ADDR, 36); + __vcpu_nested_state_set(vcpu, &state->nested); + } else { + vcpu_load_state(vcpu, state); + } /* * Restore XSAVE state in a dummy vCPU, first without doing generates: WARNING: CPU: 30 PID: 938 at arch/x86/kvm/svm/nested.c:1877 svm_set_nested_state+0x34a/0x360 [kvm_amd] Modules linked in: kvm_amd kvm irqbypass [last unloaded: kvm] CPU: 30 UID: 1000 PID: 938 Comm: state_test Tainted: G W 6.18.0-rc7-58e10b63777d-next-vm Tainted: [W]=WARN Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:svm_set_nested_state+0x34a/0x360 [kvm_amd] Call Trace: <TASK> kvm_arch_vcpu_ioctl+0xf33/0x1700 [kvm] kvm_vcpu_ioctl+0x4e6/0x8f0 [kvm] __x64_sys_ioctl+0x8f/0xd0 do_syscall_64+0x61/0xad0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Simply delete the WARN instead of trying to prevent userspace from shoving "illegal" state into CR3. For better or worse, KVM's ABI allows userspace to set CPUID after SREGS, and vice versa, and KVM is very permissive when it comes to guest CPUID. I.e. attempting to enforce the virtual CPU model when setting CPUID could break userspace. Given that the WARN doesn't provide any meaningful protection for KVM or benefit for userspace, simply drop it even though the odds of breaking userspace are minuscule. Opportunistically delete a spurious newline.

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
3.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Affected Products 6

VendorProductVersionRange
linuxlinux_kernel*≥5.14  –  <5.15.202
linuxlinux_kernel*≥5.16  –  <6.1.165
linuxlinux_kernel*≥6.2  –  <6.6.128
linuxlinux_kernel*≥6.7  –  <6.12.75
linuxlinux_kernel*≥6.13  –  <6.18.16
linuxlinux_kernel*≥6.19  –  <6.19.6

References 7

  • git.kernel.org https://git.kernel.org/stable/c/155ec243ef726f4bc49536fa0bfb565dc011ab17
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/580ea57840864d40e019bc13fd26afdc8d510a2f
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/969e5e13ff5c18603f21d1f9f64ec9194e141ac0
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ce904c8a5bbe697eae0f7e34b07095bd7a6dee19
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/fc3ba56385d03501eb582e4b86691ba378e556f9
    Patch

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/155ec243ef726f4bc49536fa0bfb565dc011ab17
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/580ea57840864d40e019bc13fd26afdc8d510a2f
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/969e5e13ff5c18603f21d1f9f64ec9194e141ac0
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ce904c8a5bbe697eae0f7e34b07095bd7a6dee19
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/fc3ba56385d03501eb582e4b86691ba378e556f9
    Patch