GHSA-23QP-F5G5-J76H
Vulnerability from github – Published: 2026-04-03 15:30 – Updated: 2026-04-23 21:31In 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. 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.
{
"affected": [],
"aliases": [
"CVE-2026-23425"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-03T14:16:28Z",
"severity": "MODERATE"
},
"details": "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\u0027s `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\u0027 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.",
"id": "GHSA-23qp-f5g5-j76h",
"modified": "2026-04-23T21:31:18Z",
"published": "2026-04-03T15:30:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23425"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7e7c2cf0024d89443a7af52e09e47b1fe634ab17"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/858620655c1fbff05997e162fc7d83a3293d5142"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bce3847f7c51b86332bf2e554c9e80ca3820f16c"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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|---|
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