{"id":"CVE-2026-23425","state":"PUBLISHED","title":"KVM: arm64: Fix ID register initialization for non-protected pKVM guests","description":"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.","publishedAt":"2026-04-03T13:24:33.384Z","updatedAt":"2026-08-05T12:21:39.120Z","severity":{"score":8.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"41d6028e28bd474298ff10409c292ec46cf43a90","status":"affected","lessThan":"bce3847f7c51b86332bf2e554c9e80ca3820f16c","versionType":"git"},{"version":"41d6028e28bd474298ff10409c292ec46cf43a90","status":"affected","lessThan":"858620655c1fbff05997e162fc7d83a3293d5142","versionType":"git"},{"version":"41d6028e28bd474298ff10409c292ec46cf43a90","status":"affected","lessThan":"7e7c2cf0024d89443a7af52e09e47b1fe634ab17","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/pkvm.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.17","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.7","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/pkvm.c"]}],"references":["https://git.kernel.org/stable/c/bce3847f7c51b86332bf2e554c9e80ca3820f16c","https://git.kernel.org/stable/c/858620655c1fbff05997e162fc7d83a3293d5142","https://git.kernel.org/stable/c/7e7c2cf0024d89443a7af52e09e47b1fe634ab17"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23425.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23425","state":"PUBLISHED","datePublished":"2026-04-03T13:24:33.384Z","dateUpdated":"2026-08-05T12:21:39.120Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:46.015Z"},"containers":{"cna":{"title":"KVM: arm64: Fix ID register initialization for non-protected pKVM guests","descriptions":[{"lang":"en","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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"41d6028e28bd474298ff10409c292ec46cf43a90","status":"affected","lessThan":"bce3847f7c51b86332bf2e554c9e80ca3820f16c","versionType":"git"},{"version":"41d6028e28bd474298ff10409c292ec46cf43a90","status":"affected","lessThan":"858620655c1fbff05997e162fc7d83a3293d5142","versionType":"git"},{"version":"41d6028e28bd474298ff10409c292ec46cf43a90","status":"affected","lessThan":"7e7c2cf0024d89443a7af52e09e47b1fe634ab17","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/pkvm.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.14","versionType":"semver"},{"version":"6.18.17","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.7","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/arm64/kvm/hyp/nvhe/pkvm.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/bce3847f7c51b86332bf2e554c9e80ca3820f16c"},{"url":"https://git.kernel.org/stable/c/858620655c1fbff05997e162fc7d83a3293d5142"},{"url":"https://git.kernel.org/stable/c/7e7c2cf0024d89443a7af52e09e47b1fe634ab17"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable pKVM path is reached by a local attacker able to create and run an arm64 KVM VM through /dev/kvm ioctls, not by network or adjacent traffic.\nAC:L - The trigger is deterministic on affected pKVM systems: create/run a non-protected VM and execute guest EL1 system-register operations; there is no attacker-uncontrolled race.\nPR:L - The attacker needs local permission to use /dev/kvm and run a VM, but the kernel path does not require real root or CAP_SYS_ADMIN once that device access exists.\nUI:N - No victim interaction is required after the attacker runs the malicious VM workload.\nS:C - The bug crosses the KVM guest/host security boundary because guest-controlled CPU system-register state can be left active when returning to the host.\nC:H - Skipped save/restore of TCR2/PIR/POR-class registers can expose stale host or other-context register state and can plausibly undermine host memory permission behavior, so the highest defensible confidentiality impact is high.\nI:H - A malicious guest can corrupt host EL1 translation and permission-overlay state across the world switch, plausibly enabling unauthorized host memory modification or control-flow compromise.\nA:H - Corrupting host MMU and permission-control registers can reliably crash or destabilize the host kernel, and the attacker can repeat the trigger via KVM_RUN."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:21:39.120Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.18.17"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"6.19.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}