198 lines
9.8 KiB
JSON
198 lines
9.8 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2021-47450",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2024-05-21T14:58:30.832Z",
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"datePublished": "2024-05-22T06:19:41.443Z",
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"dateUpdated": "2026-08-05T08:47:53.018Z"
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},
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T08:47:53.018Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Fix host stage-2 PGD refcount\n\nThe KVM page-table library refcounts the pages of concatenated stage-2\nPGDs individually. However, when running KVM in protected mode, the\nhost's stage-2 PGD is currently managed by EL2 as a single high-order\ncompound page, which can cause the refcount of the tail pages to reach 0\nwhen they shouldn't, hence corrupting the page-table.\n\nFix this by introducing a new hyp_split_page() helper in the EL2 page\nallocator (matching the kernel's split_page() function), and make use of\nit from host_s2_zalloc_pages_exact()."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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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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"baseScore": 8.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - The bug is in pKVM EL2 host stage-2 PGD refcounting and is reached via local host activity (host stage-2 faults, KVM/hyp share/donate paths), not via remote packet processing.\nAC:L - Once pKVM protected mode is enabled, emptying the last counted PTE in a concatenated PGD tail page deterministically drives that page's refcount to zero and frees it while it remains part of the live PGD; an attacker who can cause host stage-2 map/unmap churn can reliably provoke this.\nPR:L - On the primary pKVM deployment (e.g. Android), a normal local user who can drive host MMIO/KVM-related stage-2 updates can reach the vulnerable get/put_page path without needing real root in the init namespace.\nUI:N - No separate victim action is required; the attacker triggers the map/unmap sequence themselves.\nS:C - Corruption is of the EL2 host stage-2 page tables that enforce the pKVM isolation boundary between the host and the hypervisor/protected VMs, so impact crosses that security authority.\nC:H - Incorrectly freeing an in-use PGD page is a page-table UAF; reuse of that page can yield attacker-controlled stage-2 entries and arbitrary host/hyp memory disclosure across the pKVM boundary.\nI:H - The same PGD UAF enables installation of malicious stage-2 mappings and control-flow/memory integrity breaks in the hypervisor-managed host view of physical memory.\nA:H - Freeing or corrupting live host stage-2 PGD pages can panic EL2, oops the host, or otherwise crash the system."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"arch/arm64/kvm/hyp/include/nvhe/gfp.h",
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"arch/arm64/kvm/hyp/nvhe/mem_protect.c",
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"arch/arm64/kvm/hyp/nvhe/page_alloc.c"
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],
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"lessThan": "b372264c66ef78f2cab44e877fbd765ad6d24c39",
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"status": "affected",
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"versionType": "git"
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"status": "affected",
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{
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"arch/arm64/kvm/hyp/include/nvhe/gfp.h",
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"arch/arm64/kvm/hyp/nvhe/mem_protect.c",
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"arch/arm64/kvm/hyp/nvhe/page_alloc.c"
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],
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"versions": [
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{
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"version": "5.13",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "5.13",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "5.14.15",
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"lessThanOrEqual": "5.14.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "5.15",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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"references": [
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"url": "https://git.kernel.org/stable/c/b372264c66ef78f2cab44e877fbd765ad6d24c39"
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"url": "https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1"
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}
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],
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"title": "KVM: arm64: Fix host stage-2 PGD refcount",
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"content": {
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"id": "CVE-2021-47450",
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