242 lines
13 KiB
JSON
242 lines
13 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-2021-47639",
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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": "2025-02-26T01:48:21.519Z",
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"datePublished": "2025-02-26T01:54:11.651Z",
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"dateUpdated": "2026-08-05T08:48:44.903Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-08-05T08:48:44.903Z"
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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: 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>"
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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:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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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 - 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—memslot 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—so 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’s 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."
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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/x86/kvm/mmu/tdp_mmu.c"
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],
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"versions": [
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{
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"version": "b7cccd397f310739fb85383033e95580f99927e0",
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"lessThan": "af47248407c0c5ae52a752af1ab5ce5b0db91502",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "b7cccd397f310739fb85383033e95580f99927e0",
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"lessThan": "0c8a8da182d4333d9bbb9131d765145568c847b2",
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"status": "affected",
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},
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{
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"lessThan": "8cf6f98ab1d16d5e607635a0c21c4231eb15367e",
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"status": "affected",
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"lessThan": "d62007edf01f5c11f75d0f4b1e538fc52a5b1982",
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"status": "affected",
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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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/x86/kvm/mmu/tdp_mmu.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": "5.15.33",
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"lessThanOrEqual": "5.15.*",
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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": "5.16.19",
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"lessThanOrEqual": "5.16.*",
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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": "5.17.2",
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"lessThanOrEqual": "5.17.*",
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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": "5.18",
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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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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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{
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"operator": "OR",
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"negate": false,
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "5.13",
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"versionEndExcluding": "5.15.33"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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}
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/af47248407c0c5ae52a752af1ab5ce5b0db91502"
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},
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{
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"url": "https://git.kernel.org/stable/c/0c8a8da182d4333d9bbb9131d765145568c847b2"
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},
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{
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"url": "https://git.kernel.org/stable/c/8cf6f98ab1d16d5e607635a0c21c4231eb15367e"
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},
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{
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"url": "https://git.kernel.org/stable/c/d62007edf01f5c11f75d0f4b1e538fc52a5b1982"
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}
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],
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"title": "KVM: x86/mmu: Zap _all_ roots when unmapping gfn range in TDP MMU",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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"adp": [
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{
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"metrics": [
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{
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"cvssV3_1": {
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"scope": "UNCHANGED",
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"version": "3.1",
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"baseScore": 7.8,
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"attackVector": "LOCAL",
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"baseSeverity": "HIGH",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"integrityImpact": "HIGH",
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"userInteraction": "NONE",
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"attackComplexity": "LOW",
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"availabilityImpact": "HIGH",
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"privilegesRequired": "LOW",
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"confidentialityImpact": "HIGH"
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}
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},
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{
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"other": {
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"type": "ssvc",
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"content": {
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"id": "CVE-2021-47639",
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"role": "CISA Coordinator",
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"options": [
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{
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"Exploitation": "none"
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},
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{
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"Automatable": "no"
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},
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{
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"Technical Impact": "total"
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}
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],
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"version": "2.0.3",
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"timestamp": "2025-02-27T18:17:52.744634Z"
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}
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}
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}
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],
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"problemTypes": [
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{
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"descriptions": [
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{
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"lang": "en",
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"type": "CWE",
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"cweId": "CWE-416",
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"description": "CWE-416 Use After Free"
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}
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]
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}
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],
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"title": "CISA ADP Vulnrichment",
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"providerMetadata": {
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"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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"shortName": "CISA-ADP",
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"dateUpdated": "2025-02-27T18:22:35.903Z"
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}
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}
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]
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}
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} |