CVE-2026-43315
Estado: AnalizadaMedia (5.5)—
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:
generates:
Simply delete the WARN instead of trying to prevent userspace from shoving "illegal" state into CR3.
Leer descripción completaMostrar menos
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.
Detalles técnicos trazas, registros y código del informe original
--- 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
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/0x53CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.17%
- Percentil entre todas las CVEs puntuadas: 6
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
CWE
- NVD-CWE-noinfo
Referencias
- https://git.kernel.org/stable/c/155ec243ef726f4bc49536fa0bfb565dc011ab17
- https://git.kernel.org/stable/c/580ea57840864d40e019bc13fd26afdc8d510a2f
- https://git.kernel.org/stable/c/969e5e13ff5c18603f21d1f9f64ec9194e141ac0
- https://git.kernel.org/stable/c/ce904c8a5bbe697eae0f7e34b07095bd7a6dee19
- https://git.kernel.org/stable/c/deb8f6dfd31d94b18dbeeaa8c01fbec5fc70fd2b
- https://git.kernel.org/stable/c/ebb2ab4f1c87d6b52776292cf7dc16aea48e95f8
- https://git.kernel.org/stable/c/fc3ba56385d03501eb582e4b86691ba378e556f9
JSON original (NVD)
Mostrar
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"source": "nvd@nist.gov",
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"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
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"confidentialityImpact": "NONE"
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"published": "2026-05-08T14:16:39.977",
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"source": "nvd@nist.gov",
"description": [
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"value": "NVD-CWE-noinfo"
}
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: nSVM: Remove a user-triggerable WARN on nested_svm_load_cr3() succeeding\n\nDrop the WARN in svm_set_nested_state() on nested_svm_load_cr3() failing\nas it is trivially easy to trigger from userspace by modifying CPUID after\nloading CR3. E.g. modifying the state restoration selftest like so:\n\n --- tools/testing/selftests/kvm/x86/state_test.c\n +++ tools/testing/selftests/kvm/x86/state_test.c\n @@ -280,7 +280,16 @@ int main(int argc, char *argv[])\n\n /* Restore state in a new VM. */\n vcpu = vm_recreate_with_one_vcpu(vm);\n - vcpu_load_state(vcpu, state);\n +\n + if (stage == 4) {\n + state->sregs.cr3 = BIT(44);\n + vcpu_load_state(vcpu, state);\n +\n + vcpu_set_cpuid_property(vcpu, X86_PROPERTY_MAX_PHY_ADDR, 36);\n + __vcpu_nested_state_set(vcpu, &state->nested);\n + } else {\n + vcpu_load_state(vcpu, state);\n + }\n\n /*\n * Restore XSAVE state in a dummy vCPU, first without doing\n\ngenerates:\n\n WARNING: CPU: 30 PID: 938 at arch/x86/kvm/svm/nested.c:1877 svm_set_nested_state+0x34a/0x360 [kvm_amd]\n Modules linked in: kvm_amd kvm irqbypass [last unloaded: kvm]\n CPU: 30 UID: 1000 PID: 938 Comm: state_test Tainted: G W 6.18.0-rc7-58e10b63777d-next-vm\n Tainted: [W]=WARN\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:svm_set_nested_state+0x34a/0x360 [kvm_amd]\n Call Trace:\n <TASK>\n kvm_arch_vcpu_ioctl+0xf33/0x1700 [kvm]\n kvm_vcpu_ioctl+0x4e6/0x8f0 [kvm]\n __x64_sys_ioctl+0x8f/0xd0\n do_syscall_64+0x61/0xad0\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\nSimply delete the WARN instead of trying to prevent userspace from shoving\n\"illegal\" state into CR3. For better or worse, KVM's ABI allows userspace\nto set CPUID after SREGS, and vice versa, and KVM is very permissive when\nit comes to guest CPUID. I.e. attempting to enforce the virtual CPU model\nwhen setting CPUID could break userspace. Given that the WARN doesn't\nprovide any meaningful protection for KVM or benefit for userspace, simply\ndrop it even though the odds of breaking userspace are minuscule.\n\nOpportunistically delete a spurious newline."
}
],
"lastModified": "2026-06-17T10:49:22.003",
"configurations": [
{
"nodes": [
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}