298 lines
16 KiB
JSON
298 lines
16 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-2026-72170",
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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": "2026-08-09T03:40:39.910Z",
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"datePublished": "2026-08-15T05:53:36.332Z",
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"dateUpdated": "2026-10-16T18:45:00.097Z"
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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": "2026-08-23T12:46:59.271Z"
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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\n9p: skip nlink update in cacheless mode to fix WARN_ON\n\nv9fs_dec_count() unconditionally calls drop_nlink() on regular files,\neven when the inode's nlink is already zero. In cacheless mode the\nclient refetches inode metadata from the server (the source of truth)\non every operation, so by the time v9fs_remove() returns, the locally\ncached nlink may already reflect the post-unlink value:\n\n 1. Client initiates unlink, server processes it and sets nlink to 0\n 2. Client refetches inode metadata (nlink=0) before unlink returns\n 3. Client's v9fs_remove() completes successfully\n 4. Client calls v9fs_dec_count() which calls drop_nlink() on nlink=0\n\nThis race is easily triggered under heavy unlink workloads, such as\nstress-ng's unlink stressor, producing the following warning:\n\n WARNING: fs/inode.c:417 at drop_nlink+0x4c/0xc8\n Call trace:\n drop_nlink+0x4c/0xc8\n v9fs_remove+0x1e0/0x250 [9p]\n v9fs_vfs_unlink+0x20/0x38 [9p]\n vfs_unlink+0x13c/0x258\n ...\n\nIn cacheless mode the server is authoritative and the inode is on its\nway out, so locally adjusting nlink buys nothing. Skip v9fs_dec_count()\nentirely when neither CACHE_META nor CACHE_LOOSE is set, which both\navoids the warning and removes a class of nlink races (two concurrent\nunlinkers observing nlink > 0 and both calling drop_nlink()) that an\nnlink == 0 guard alone would only narrow rather than close."
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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 - Triggered via unlink/rmdir/rename syscalls on a mounted 9p client filesystem (default cacheless mode). Common in QEMU/KVM virtio-9p guest shares and TCP-mounted exports; requires code execution on the client host, not direct remote packet delivery to this kernel path.\nAC:L - The fix commit states the race is easily triggered under heavy unlink workloads (e.g., stress-ng). An attacker can drive concurrent unlinks or getattr/unlink on the same inode to refresh server nlink=0 before drop_nlink(), controlling both sides of the race.\nPR:L - Exploitation requires only normal filesystem write permission on the 9p export (may_delete_dentry/inode_permission on the parent directory). Guest users on virtio-9p shares or tenants with write access do not need root/CAP_SYS_ADMIN beyond using an already-mounted filesystem.\nUI:N - No victim interaction is required beyond the attacker (or compromised local process) issuing unlink/rmdir/rename on paths they can already write; mounting 9p is an admin setup step, not per-exploit user action.\nS:U - The bug corrupts inode metadata in the 9p client kernel on the same host as the attacker process. It does not cross VM/host, container/host, or IOMMU security boundaries; virtio-9p guest triggers affect the guest kernel only.\nC:H - drop_nlink() on i_nlink==0 emits WARN_ON then underflows the unsigned link counter to UINT_MAX, corrupting kernel inode metadata. Per kernel CVSS guidance, memory/metadata corruption that could be leveraged for further exploitation warrants High confidentiality.\nI:H - Unsigned i_nlink underflow corrupts inode lifecycle accounting, preventing correct removal tracking (s_remove_count) and desynchronizing dentry unlink from inode state. This class of VFS inode corruption can enable further integrity violations and is scored High when uncertain.\nA:H - Each hit triggers kernel WARN_ON (easily spammed for denial-of-service via log flooding, and fatal where panic_on_warn is enabled) and leaves inodes with bogus nlink values that can provoke subsequent kernel faults during VFS operations on affected files."
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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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"fs/9p/vfs_inode.c"
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],
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"versions": [
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{
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"version": "ac89b2ef9b55924bcf922251f043ba73a32d05bb",
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"status": "affected",
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"status": "affected",
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"status": "affected",
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"version": "ac89b2ef9b55924bcf922251f043ba73a32d05bb",
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"lessThan": "8d610017c992de705b304d3d727a6e3a86af6149",
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"status": "affected",
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"lessThan": "8faccac11e1369adddf5d80f4a45af93f13b2e1a",
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"status": "affected",
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"version": "ac89b2ef9b55924bcf922251f043ba73a32d05bb",
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"lessThan": "574aa0b4799470ac814479f1138d19efe6262255",
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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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"fs/9p/vfs_inode.c"
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],
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{
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"version": "4.17",
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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": "4.17",
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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": "5.10.266",
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"lessThanOrEqual": "5.10.*",
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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": "5.15.217",
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"lessThanOrEqual": "5.15.*",
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"status": "unaffected",
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},
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{
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"version": "6.1.184",
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"lessThanOrEqual": "6.1.*",
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"status": "unaffected",
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},
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"version": "6.6.145",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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},
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{
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"version": "6.12.97",
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"lessThanOrEqual": "6.12.*",
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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": "6.18.40",
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"lessThanOrEqual": "6.18.*",
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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": "7.1.5",
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"lessThanOrEqual": "7.1.*",
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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": "7.2",
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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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"cpeApplicability": [
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"references": [
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"url": "https://git.kernel.org/stable/c/6086469f7d469549bfd070348b717a6e43736200"
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},
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"url": "https://git.kernel.org/stable/c/a5a682b016ef5b5384e28f6d652d47a8f8e73d37"
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},
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{
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},
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{
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"url": "https://git.kernel.org/stable/c/8d610017c992de705b304d3d727a6e3a86af6149"
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},
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{
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"url": "https://git.kernel.org/stable/c/8faccac11e1369adddf5d80f4a45af93f13b2e1a"
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},
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{
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"url": "https://git.kernel.org/stable/c/574aa0b4799470ac814479f1138d19efe6262255"
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}
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],
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"title": "9p: skip nlink update in cacheless mode to fix WARN_ON",
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"x_generator": {
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"engine": "bippy-1.2.0"
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}
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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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"other": {
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"type": "ssvc",
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"content": {
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"id": "CVE-2026-72170",
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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": "2026-10-16T18:43:16.365463Z"
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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": "2026-10-16T18:45:00.097Z"
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}
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}
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]
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}
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} |