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CVE-2026-43315

Vulnérabilité non évaluée dans Linux (Linux)

CVSS 0.0 · Non évaluée
EPSS 0.2%
Linux•Linux•Versions : <ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8, <=6.1.*, <155ec243ef726f4bc49536fa0bfb565dc011ab17, <=6.12.*, <969e5e13ff5c18603f21d1f9f64ec9194e141ac0, <ce904c8a5bbe697eae0f7e34b07095bd7a6dee19, <580ea57840864d40e019bc13fd26afdc8d510a2f, 0, 7.0, 6.1.165, 6.12.75, <5.14, <=6.6.*, 5.14, <=6.19.*, b222b0b88162bdef4eceb12a79d5edbbdb23dbfd, <=6.18.*, 6.19.6, 6.6.128, 6.18.16, <=*, <=5.15.*, <deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b, 5.15.202, <fc3ba56385d03501eb582e4b86691ba378e556f9

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.

Gravité et risque d'exploitation

CVE-2026-43315 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.17 %, ce qui la place devant 6.3 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8, <=6.1.*, <155ec243ef726f4bc49536fa0bfb565dc011ab17, <=6.12.*, <969e5e13ff5c18603f21d1f9f64ec9194e141ac0, <ce904c8a5bbe697eae0f7e34b07095bd7a6dee19, <580ea57840864d40e019bc13fd26afdc8d510a2f, 0, 7.0, 6.1.165, 6.12.75, <5.14, <=6.6.*, 5.14, <=6.19.*, b222b0b88162bdef4eceb12a79d5edbbdb23dbfd, <=6.18.*, 6.19.6, 6.6.128, 6.18.16, <=*, <=5.15.*, <deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b, 5.15.202, <fc3ba56385d03501eb582e4b86691ba378e556f9) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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