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CVE-2026-23425

Estado: ModificadaMedia (5.5)—

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: Fix ID register initialization for non-protected pKVM guests

In protected mode, the hypervisor maintains a separate instance of the `kvm` structure for each VM. For non-protected VMs, this structure is initialized from the host's `kvm` state.

Currently, `pkvm_init_features_from_host()` copies the `KVM_ARCH_FLAG_ID_REGS_INITIALIZED` flag from the host without the underlying `id_regs` data being initialized. This results in the hypervisor seeing the flag as set while the ID registers remain zeroed.

Consequently, `kvm_has_feat()` checks at EL2 fail (return 0) for non-protected VMs. This breaks logic that relies on feature detection, such as `ctxt_has_tcrx()` for TCR2_EL1 support.

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As a result, certain system registers (e.g., TCR2_EL1, PIR_EL1, POR_EL1) are not saved/restored during the world switch, which could lead to state corruption.

Fix this by explicitly copying the ID registers from the host `kvm` to the hypervisor `kvm` for non-protected VMs during initialization, since we trust the host with its non-protected guests' features. Also ensure `KVM_ARCH_FLAG_ID_REGS_INITIALIZED` is cleared initially in `pkvm_init_features_from_host` so that `vm_copy_id_regs` can properly initialize them and set the flag once done.

CVSS

Probabilidad de explotación (EPSS)

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)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-23425",
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          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Fix ID register initialization for non-protected pKVM guests\n\nIn protected mode, the hypervisor maintains a separate instance of\nthe `kvm` structure for each VM. For non-protected VMs, this structure is\ninitialized from the host's `kvm` state.\n\nCurrently, `pkvm_init_features_from_host()` copies the\n`KVM_ARCH_FLAG_ID_REGS_INITIALIZED` flag from the host without the\nunderlying `id_regs` data being initialized. This results in the\nhypervisor seeing the flag as set while the ID registers remain zeroed.\n\nConsequently, `kvm_has_feat()` checks at EL2 fail (return 0) for\nnon-protected VMs. This breaks logic that relies on feature detection,\nsuch as `ctxt_has_tcrx()` for TCR2_EL1 support. As a result, certain\nsystem registers (e.g., TCR2_EL1, PIR_EL1, POR_EL1) are not\nsaved/restored during the world switch, which could lead to state\ncorruption.\n\nFix this by explicitly copying the ID registers from the host `kvm` to\nthe hypervisor `kvm` for non-protected VMs during initialization, since\nwe trust the host with its non-protected guests' features. Also ensure\n`KVM_ARCH_FLAG_ID_REGS_INITIALIZED` is cleared initially in\n`pkvm_init_features_from_host` so that `vm_copy_id_regs` can properly\ninitialize them and set the flag once done."
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      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nKVM: arm64: Corrección de la inicialización de registros ID para invitados pKVM no protegidos\n\nEn modo protegido, el hipervisor mantiene una instancia separada de la estructura 'kvm' para cada VM. Para VMs no protegidas, esta estructura se inicializa a partir del estado 'kvm' del host.\n\nActualmente, 'pkvm_init_features_from_host()' copia el flag 'KVM_ARCH_FLAG_ID_REGS_INITIALIZED' del host sin que los datos subyacentes de 'id_regs' se inicialicen. Esto resulta en que el hipervisor ve el flag como establecido mientras los registros ID permanecen a cero.\n\nConsecuentemente, las comprobaciones de 'kvm_has_feat()' en EL2 fallan (devuelven 0) para VMs no protegidas. Esto rompe la lógica que depende de la detección de características, como 'ctxt_has_tcrx()' para el soporte de TCR2_EL1. Como resultado, ciertos registros del sistema (p. ej., TCR2_EL1, PIR_EL1, POR_EL1) no se guardan/restauran durante el world switch, lo que podría llevar a la corrupción del estado.\n\nEsto se soluciona copiando explícitamente los registros ID del 'kvm' del host al 'kvm' del hipervisor para VMs no protegidas durante la inicialización, ya que confiamos en el host con las características de sus invitados no protegidos. También se debe asegurar que 'KVM_ARCH_FLAG_ID_REGS_INITIALIZED' se borre inicialmente en 'pkvm_init_features_from_host' para que 'vm_copy_id_regs' pueda inicializarlos correctamente y establecer el flag una vez terminado."
    }
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  "lastModified": "2026-07-21T19:10:00.107",
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