CVE-2021-47639

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2021-47639", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-02-26T01:48:21.519Z", "datePublished": "2025-02-26T01:54:11.651Z", "dateUpdated": "2026-08-05T08:48:44.903Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:48:44.903Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU\n\nZap both valid and invalid roots when zapping/unmapping a gfn range, as\nKVM must ensure it holds no references to the freed page after returning\nfrom the unmap operation. Most notably, the TDP MMU doesn't zap invalid\nroots in mmu_notifier callbacks. This leads to use-after-free and other\nissues if the mmu_notifier runs to completion while an invalid root\nzapper yields as KVM fails to honor the requirement that there must be\n_no_ references to the page after the mmu_notifier returns.\n\nThe bug is most easily reproduced by hacking KVM to cause a collision\nbetween set_nx_huge_pages() and kvm_mmu_notifier_release(), but the bug\nexists between kvm_mmu_notifier_invalidate_range_start() and memslot\nupdates as well. Invalidating a root ensures pages aren't accessible by\nthe guest, and KVM won't read or write page data itself, but KVM will\ntrigger e.g. kvm_set_pfn_dirty() when zapping SPTEs, and thus completing\na zap of an invalid root _after_ the mmu_notifier returns is fatal.\n\n WARNING: CPU: 24 PID: 1496 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:173 [kvm]\n RIP: 0010:kvm_is_zone_device_pfn+0x96/0xa0 [kvm]\n Call Trace:\n <TASK>\n kvm_set_pfn_dirty+0xa8/0xe0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n zap_gfn_range+0x1f3/0x310 [kvm]\n kvm_tdp_mmu_zap_invalidated_roots+0x50/0x90 [kvm]\n kvm_mmu_zap_all_fast+0x177/0x1a0 [kvm]\n set_nx_huge_pages+0xb4/0x190 [kvm]\n param_attr_store+0x70/0x100\n module_attr_store+0x19/0x30\n kernfs_fop_write_iter+0x119/0x1b0\n new_sync_write+0x11c/0x1b0\n vfs_write+0x1cc/0x270\n ksys_write+0x5f/0xe0\n do_syscall_64+0x38/0xc0\n entry_SYSCALL_64_after_hwframe+0x44/0xae\n </TASK>"}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - Exploitation requires local access to /dev/kvm to create a VM and issue memslot updates (KVM_SET_USER_MEMORY_REGION) while concurrently unmapping guest backing memory; it is not reachable via network packets or pure guest execution without host VMM control.\nAC:L - The attacker controls both sides of the race\u2014memslot delete/move triggering kvm_mmu_zap_all_fast (which yields in kvm_tdp_mmu_zap_invalidated_roots) and munmap/madvise triggering mmu_notifier_invalidate_range_start\u2014so the race can be induced reliably without depending on external conditions.\nPR:L - Triggering requires only an unprivileged local account able to open /dev/kvm (e.g., kvm-group membership or nested-virt deployments), not real root/CAP_SYS_ADMIN in the init namespace.\nUI:N - The attacker directly drives the ioctls and memory unmap operations; no separate victim user action is required.\nS:U - This is a host userspace-to-host-kernel privilege escalation via KVM ioctls, not a guest-to-host escape; the impact remains within the host kernel\u2019s security authority.\nC:H - The bug is a use-after-free on host page/SPTE state (kvm_set_pfn_dirty on PFNs after mmu_notifier completion), which can be leveraged for arbitrary kernel memory disclosure via heap reuse.\nI:H - The same UAF on freed page structures during delayed invalid-root zapping provides a path to arbitrary kernel writes and control-flow hijacking once the freed memory is reallocated.\nA:H - The UAF reliably produces kernel WARN/oops paths (e.g., kvm_is_zone_device_pfn on pages with zero refcount) and can crash or hang the host even when not fully exploited."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/mmu/tdp_mmu.c"], "versions": [{"version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "af47248407c0c5ae52a752af1ab5ce5b0db91502", "status": "affected", "versionType": "git"}, {"version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "0c8a8da182d4333d9bbb9131d765145568c847b2", "status": "affected", "versionType": "git"}, {"version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "8cf6f98ab1d16d5e607635a0c21c4231eb15367e", "status": "affected", "versionType": "git"}, {"version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "d62007edf01f5c11f75d0f4b1e538fc52a5b1982", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/mmu/tdp_mmu.c"], "versions": [{"version": "5.13", "status": "affected"}, {"version": "0", "lessThan": "5.13", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.33", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.16.19", "lessThanOrEqual": "5.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.17.2", "lessThanOrEqual": "5.17.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.18", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.15.33"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.16.19"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.17.2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.13", "versionEndExcluding": "5.18"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/af47248407c0c5ae52a752af1ab5ce5b0db91502"}, {"url": "https://git.kernel.org/stable/c/0c8a8da182d4333d9bbb9131d765145568c847b2"}, {"url": "https://git.kernel.org/stable/c/8cf6f98ab1d16d5e607635a0c21c4231eb15367e"}, {"url": "https://git.kernel.org/stable/c/d62007edf01f5c11f75d0f4b1e538fc52a5b1982"}], "title": "KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2021-47639", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2025-02-27T18:17:52.744634Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-416", "description": "CWE-416 Use After Free"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-02-27T18:22:35.903Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.8, "attackVector": "LOCAL", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "integrityImpact": "HIGH", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2021-47639", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2025-02-27T18:17:52.744634Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-416", "description": "CWE-416 Use After Free"}]}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-02-27T18:17:54.139Z"}}], "cna": {"title": "KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU", "metrics": [{"cvssV3_1": {"version": "3.1", "baseScore": 7.8, "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}, "scenarios": [{"lang": "en", "value": "AV:L - Exploitation requires local access to /dev/kvm to create a VM and issue memslot updates (KVM_SET_USER_MEMORY_REGION) while concurrently unmapping guest backing memory; it is not reachable via network packets or pure guest execution without host VMM control.\nAC:L - The attacker controls both sides of the race\u2014memslot delete/move triggering kvm_mmu_zap_all_fast (which yields in kvm_tdp_mmu_zap_invalidated_roots) and munmap/madvise triggering mmu_notifier_invalidate_range_start\u2014so the race can be induced reliably without depending on external conditions.\nPR:L - Triggering requires only an unprivileged local account able to open /dev/kvm (e.g., kvm-group membership or nested-virt deployments), not real root/CAP_SYS_ADMIN in the init namespace.\nUI:N - The attacker directly drives the ioctls and memory unmap operations; no separate victim user action is required.\nS:U - This is a host userspace-to-host-kernel privilege escalation via KVM ioctls, not a guest-to-host escape; the impact remains within the host kernel\u2019s security authority.\nC:H - The bug is a use-after-free on host page/SPTE state (kvm_set_pfn_dirty on PFNs after mmu_notifier completion), which can be leveraged for arbitrary kernel memory disclosure via heap reuse.\nI:H - The same UAF on freed page structures during delayed invalid-root zapping provides a path to arbitrary kernel writes and control-flow hijacking once the freed memory is reallocated.\nA:H - The UAF reliably produces kernel WARN/oops paths (e.g., kvm_is_zone_device_pfn on pages with zero refcount) and can crash or hang the host even when not fully exploited."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "af47248407c0c5ae52a752af1ab5ce5b0db91502", "versionType": "git"}, {"status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "0c8a8da182d4333d9bbb9131d765145568c847b2", "versionType": "git"}, {"status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "8cf6f98ab1d16d5e607635a0c21c4231eb15367e", "versionType": "git"}, {"status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "lessThan": "d62007edf01f5c11f75d0f4b1e538fc52a5b1982", "versionType": "git"}], "programFiles": ["arch/x86/kvm/mmu/tdp_mmu.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "5.13"}, {"status": "unaffected", "version": "0", "lessThan": "5.13", "versionType": "semver"}, {"status": "unaffected", "version": "5.15.33", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "5.16.19", "versionType": "semver", "lessThanOrEqual": "5.16.*"}, {"status": "unaffected", "version": "5.17.2", "versionType": "semver", "lessThanOrEqual": "5.17.*"}, {"status": "unaffected", "version": "5.18", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["arch/x86/kvm/mmu/tdp_mmu.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/af47248407c0c5ae52a752af1ab5ce5b0db91502"}, {"url": "https://git.kernel.org/stable/c/0c8a8da182d4333d9bbb9131d765145568c847b2"}, {"url": "https://git.kernel.org/stable/c/8cf6f98ab1d16d5e607635a0c21c4231eb15367e"}, {"url": "https://git.kernel.org/stable/c/d62007edf01f5c11f75d0f4b1e538fc52a5b1982"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU\n\nZap both valid and invalid roots when zapping/unmapping a gfn range, as\nKVM must ensure it holds no references to the freed page after returning\nfrom the unmap operation. Most notably, the TDP MMU doesn't zap invalid\nroots in mmu_notifier callbacks. This leads to use-after-free and other\nissues if the mmu_notifier runs to completion while an invalid root\nzapper yields as KVM fails to honor the requirement that there must be\n_no_ references to the page after the mmu_notifier returns.\n\nThe bug is most easily reproduced by hacking KVM to cause a collision\nbetween set_nx_huge_pages() and kvm_mmu_notifier_release(), but the bug\nexists between kvm_mmu_notifier_invalidate_range_start() and memslot\nupdates as well. Invalidating a root ensures pages aren't accessible by\nthe guest, and KVM won't read or write page data itself, but KVM will\ntrigger e.g. kvm_set_pfn_dirty() when zapping SPTEs, and thus completing\na zap of an invalid root _after_ the mmu_notifier returns is fatal.\n\n WARNING: CPU: 24 PID: 1496 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:173 [kvm]\n RIP: 0010:kvm_is_zone_device_pfn+0x96/0xa0 [kvm]\n Call Trace:\n <TASK>\n kvm_set_pfn_dirty+0xa8/0xe0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n zap_gfn_range+0x1f3/0x310 [kvm]\n kvm_tdp_mmu_zap_invalidated_roots+0x50/0x90 [kvm]\n kvm_mmu_zap_all_fast+0x177/0x1a0 [kvm]\n set_nx_huge_pages+0xb4/0x190 [kvm]\n param_attr_store+0x70/0x100\n module_attr_store+0x19/0x30\n kernfs_fop_write_iter+0x119/0x1b0\n new_sync_write+0x11c/0x1b0\n vfs_write+0x1cc/0x270\n ksys_write+0x5f/0xe0\n do_syscall_64+0x38/0xc0\n entry_SYSCALL_64_after_hwframe+0x44/0xae\n </TASK>"}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.33", "versionStartIncluding": "5.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.16.19", "versionStartIncluding": "5.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.17.2", "versionStartIncluding": "5.13"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.18", "versionStartIncluding": "5.13"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T08:48:44.903Z"}}}, "cveMetadata": {"cveId": "CVE-2021-47639", "state": "PUBLISHED", "dateUpdated": "2026-08-05T08:48:44.903Z", "dateReserved": "2025-02-26T01:48:21.519Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2025-02-26T01:54:11.651Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["arch/x86/kvm/mmu/tdp_mmu.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "af47248407c0c5ae52a752af1ab5ce5b0db91502", "status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "versionType": "git"}, {"lessThan": "0c8a8da182d4333d9bbb9131d765145568c847b2", "status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "versionType": "git"}, {"lessThan": "8cf6f98ab1d16d5e607635a0c21c4231eb15367e", "status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "versionType": "git"}, {"lessThan": "d62007edf01f5c11f75d0f4b1e538fc52a5b1982", "status": "affected", "version": "b7cccd397f310739fb85383033e95580f99927e0", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["arch/x86/kvm/mmu/tdp_mmu.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.13"}, {"lessThan": "5.13", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.33", "versionType": "semver"}, {"lessThanOrEqual": "5.16.*", "status": "unaffected", "version": "5.16.19", "versionType": "semver"}, {"lessThanOrEqual": "5.17.*", "status": "unaffected", "version": "5.17.2", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "5.18", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "3635E21D-6C8E-41E4-BF98-89A503BAF23D", "versionEndExcluding": "5.15.33", "versionStartIncluding": "5.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "20C43679-0439-405A-B97F-685BEE50613B", "versionEndExcluding": "5.16.19", "versionStartIncluding": "5.16", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "210C679C-CF84-44A3-8939-E629C87E54BF", "versionEndExcluding": "5.17.2", "versionStartIncluding": "5.17", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU\n\nZap both valid and invalid roots when zapping/unmapping a gfn range, as\nKVM must ensure it holds no references to the freed page after returning\nfrom the unmap operation. Most notably, the TDP MMU doesn't zap invalid\nroots in mmu_notifier callbacks. This leads to use-after-free and other\nissues if the mmu_notifier runs to completion while an invalid root\nzapper yields as KVM fails to honor the requirement that there must be\n_no_ references to the page after the mmu_notifier returns.\n\nThe bug is most easily reproduced by hacking KVM to cause a collision\nbetween set_nx_huge_pages() and kvm_mmu_notifier_release(), but the bug\nexists between kvm_mmu_notifier_invalidate_range_start() and memslot\nupdates as well. Invalidating a root ensures pages aren't accessible by\nthe guest, and KVM won't read or write page data itself, but KVM will\ntrigger e.g. kvm_set_pfn_dirty() when zapping SPTEs, and thus completing\na zap of an invalid root _after_ the mmu_notifier returns is fatal.\n\n WARNING: CPU: 24 PID: 1496 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:173 [kvm]\n RIP: 0010:kvm_is_zone_device_pfn+0x96/0xa0 [kvm]\n Call Trace:\n <TASK>\n kvm_set_pfn_dirty+0xa8/0xe0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n __handle_changed_spte+0x2ab/0x5e0 [kvm]\n zap_gfn_range+0x1f3/0x310 [kvm]\n kvm_tdp_mmu_zap_invalidated_roots+0x50/0x90 [kvm]\n kvm_mmu_zap_all_fast+0x177/0x1a0 [kvm]\n set_nx_huge_pages+0xb4/0x190 [kvm]\n param_attr_store+0x70/0x100\n module_attr_store+0x19/0x30\n kernfs_fop_write_iter+0x119/0x1b0\n new_sync_write+0x11c/0x1b0\n vfs_write+0x1cc/0x270\n ksys_write+0x5f/0xe0\n do_syscall_64+0x38/0xc0\n entry_SYSCALL_64_after_hwframe+0x44/0xae\n </TASK>"}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: KVM: x86/mmu: Se eliminan _todos_ las ra\u00edces al anular la asignaci\u00f3n del rango gfn en TDP MMU Se eliminan las ra\u00edces v\u00e1lidas e inv\u00e1lidas al hacer zapping/anular la asignaci\u00f3n de un rango gfn, ya que KVM debe asegurarse de que no contiene referencias a la p\u00e1gina liberada despu\u00e9s de regresar de la operaci\u00f3n de anulaci\u00f3n de la asignaci\u00f3n. En particular, TDP MMU no elimina las ra\u00edces inv\u00e1lidas en las devoluciones de llamadas mmu_notifier. Esto conduce a problemas de use-after-free y otros problemas si mmu_notifier se ejecuta hasta el final mientras que un zapper de ra\u00edz inv\u00e1lida cede, ya que KVM no cumple con el requisito de que no debe haber _ninguna_ referencia a la p\u00e1gina despu\u00e9s de que mmu_notifier regrese. El error se reproduce m\u00e1s f\u00e1cilmente pirateando KVM para provocar una colisi\u00f3n entre set_nx_huge_pages() y kvm_mmu_notifier_release(), pero el error tambi\u00e9n existe entre kvm_mmu_notifier_invalidate_range_start() y las actualizaciones de memslot. Invalidar una ra\u00edz garantiza que el invitado no pueda acceder a las p\u00e1ginas, y KVM no leer\u00e1 ni escribir\u00e1 datos de p\u00e1gina por s\u00ed mismo, pero KVM activar\u00e1, por ejemplo, kvm_set_pfn_dirty() al hacer zapping de SPTE, y por lo tanto, completar un zapping de una ra\u00edz no v\u00e1lida _despu\u00e9s_ de que mmu_notifier regrese es fatal. ADVERTENCIA: CPU: 24 PID: 1496 en arch/x86/kvm/../../../virt/kvm/kvm_main.c:173 [kvm] RIP: 0010:kvm_is_zone_device_pfn+0x96/0xa0 [kvm] Rastreo de llamadas: kvm_set_pfn_dirty+0xa8/0xe0 [kvm] __handle_changed_spte+0x2ab/0x5e0 [kvm] __handle_changed_spte+0x2ab/0x5e0 [kvm] __handle_changed_spte+0x2ab/0x5e0 [kvm] zap_gfn_range+0x1f3/0x310 [kvm] kvm_tdp_mmu_zap_ra\u00edces_invalidadas+0x50/0x90 [kvm] kvm_mmu_zap_all_fast+0x177/0x1a0 [kvm] set_nx_huge_pages+0xb4/0x190 [kvm] param_attr_store+0x70/0x100 module_attr_store+0x19/0x30 kernfs_fop_write_iter+0x119/0x1b0 new_sync_write+0x11c/0x1b0 vfs_write+0x1cc/0x270 ksys_write+0x5f/0xe0 do_syscall_64+0x38/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae "}], "id": "CVE-2021-47639", "lastModified": "2026-06-17T04:18:13.050", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47639", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2025-02-27T18:17:52.744634Z", "version": "2.0.3"}}]}, "published": "2025-02-26T06:37:05.677", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0c8a8da182d4333d9bbb9131d765145568c847b2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/8cf6f98ab1d16d5e607635a0c21c4231eb15367e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/af47248407c0c5ae52a752af1ab5ce5b0db91502"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d62007edf01f5c11f75d0f4b1e538fc52a5b1982"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"affected_release": [{"advisory": "RHSA-2022:7683", "cpe": "cpe:/o:redhat:enterprise_linux:8", "package": "kernel-0:4.18.0-425.3.1.el8", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2022-11-08T00:00:00Z"}, {"advisory": "RHSA-2022:8267", "cpe": "cpe:/a:redhat:enterprise_linux:9", "package": "kernel-0:5.14.0-162.6.1.el9_1", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2022-11-15T00:00:00Z"}, {"advisory": "RHSA-2022:8267", "cpe": "cpe:/o:redhat:enterprise_linux:9", "package": "kernel-0:5.14.0-162.6.1.el9_1", "product_name": "Red Hat Enterprise Linux 9", "release_date": "2022-11-15T00:00:00Z"}], "bugzilla": {"description": "kernel: KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU", "id": "2348067", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2348067"}, "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": "verified"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nKVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU\nZap both valid and invalid roots when zapping/unmapping a gfn range, as\nKVM must ensure it holds no references to the freed page after returning\nfrom the unmap operation. Most notably, the TDP MMU doesn't zap invalid\nroots in mmu_notifier callbacks. This leads to use-after-free and other\nissues if the mmu_notifier runs to completion while an invalid root\nzapper yields as KVM fails to honor the requirement that there must be\n_no_ references to the page after the mmu_notifier returns.\nThe bug is most easily reproduced by hacking KVM to cause a collision\nbetween set_nx_huge_pages() and kvm_mmu_notifier_release(), but the bug\nexists between kvm_mmu_notifier_invalidate_range_start() and memslot\nupdates as well. Invalidating a root ensures pages aren't accessible by\nthe guest, and KVM won't read or write page data itself, but KVM will\ntrigger e.g. kvm_set_pfn_dirty() when zapping SPTEs, and thus completing\na zap of an invalid root _after_ the mmu_notifier returns is fatal.\nWARNING: CPU: 24 PID: 1496 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:173 [kvm]\nRIP: 0010:kvm_is_zone_device_pfn+0x96/0xa0 [kvm]\nCall Trace:\n<TASK>\nkvm_set_pfn_dirty+0xa8/0xe0 [kvm]\n__handle_changed_spte+0x2ab/0x5e0 [kvm]\n__handle_changed_spte+0x2ab/0x5e0 [kvm]\n__handle_changed_spte+0x2ab/0x5e0 [kvm]\nzap_gfn_range+0x1f3/0x310 [kvm]\nkvm_tdp_mmu_zap_invalidated_roots+0x50/0x90 [kvm]\nkvm_mmu_zap_all_fast+0x177/0x1a0 [kvm]\nset_nx_huge_pages+0xb4/0x190 [kvm]\nparam_attr_store+0x70/0x100\nmodule_attr_store+0x19/0x30\nkernfs_fop_write_iter+0x119/0x1b0\nnew_sync_write+0x11c/0x1b0\nvfs_write+0x1cc/0x270\nksys_write+0x5f/0xe0\ndo_syscall_64+0x38/0xc0\nentry_SYSCALL_64_after_hwframe+0x44/0xae\n</TASK>"], "name": "CVE-2021-47639", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"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": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-02-26T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47639\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47639\nhttps://lore.kernel.org/linux-cve-announce/2025022647-CVE-2021-47639-9183@gregkh/T"], "threat_severity": "Low"}

{}