CVE-2021-47450

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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()."}, {"lang": "es", "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: KVM: arm64: corrige el recuento de PGD de etapa 2 del host La librer\u00eda de tablas de p\u00e1ginas de KVM vuelve a contar las p\u00e1ginas de los PGD de etapa 2 concatenados individualmente. Sin embargo, cuando se ejecuta KVM en modo protegido, EL2 administra actualmente el PGD de etapa 2 del host como una \u00fanica p\u00e1gina compuesta de alto orden, lo que puede causar que el recuento de las p\u00e1ginas finales llegue a 0 cuando no deber\u00eda, corrompiendo as\u00ed el tabla de p\u00e1ginas. Solucione este problema introduciendo un nuevo asistente hyp_split_page() en el asignador de p\u00e1ginas EL2 (que coincida con la funci\u00f3n split_page() del kernel) y util\u00edcelo desde host_s2_zalloc_pages_exact()."}], "id": "CVE-2021-47450", "lastModified": "2026-08-04T10:17:03.943", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 8.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.0, "impactScore": 6.0, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47450", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-05-22T18:46:22.813390Z", "version": "2.0.3"}}]}, "published": "2024-05-22T07:15:10.143", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b372264c66ef78f2cab44e877fbd765ad6d24c39"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/1d58a17ef54599506d44c45ac95be27273a4d2b1"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b372264c66ef78f2cab44e877fbd765ad6d24c39"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-Other"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: KVM: arm64: Fix host stage-2 PGD refcount", "id": "2282909", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2282909"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-99", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nKVM: arm64: Fix host stage-2 PGD refcount\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.\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()."], "name": "CVE-2021-47450", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2024-05-22T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47450\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47450\nhttps://lore.kernel.org/linux-cve-announce/2024052242-CVE-2021-47450-c72f@gregkh/T"], "threat_severity": "Low"}

{"created": "2025-07-12T22:31:06.431980+00:00", "updated": "2025-07-12T22:31:06.432053+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}