311 lines
17 KiB
JSON
311 lines
17 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-2026-74621",
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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": "2026-08-15T05:44:03.921Z",
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"datePublished": "2026-08-22T15:32:04.990Z",
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"dateUpdated": "2026-10-16T19:06:02.607Z"
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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": "2026-08-25T05:40:45.894Z"
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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\nnet/sched: act_ct: fix sk_buff leak when the header checks reject a packet\n\ntcf_ct_handle_fragments() runs its header sanity checks before handing\nanything to the defragmentation engine:\n\n\tif (family == NFPROTO_IPV4)\n\t\terr = tcf_ct_ipv4_is_fragment(skb, &frag);\n\telse\n\t\terr = tcf_ct_ipv6_is_fragment(skb, &frag);\n\tif (err || !frag)\n\t\treturn err;\n\ntcf_ct_ipv4_is_fragment() returns -EINVAL or -ENOMEM;\ntcf_ct_ipv6_is_fragment() adds -EPROTO when ipv6_find_hdr() fails. None of\nthem frees or queues the skb, so on that path the caller still owns it.\n\ntcf_ct_act() however funnels every non-zero return into the\nownership-transfer exit:\n\n\terr = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag);\n\tif (err)\n\t\tgoto out_frag;\n\t...\nout_frag:\n\tif (err != -EINPROGRESS)\n\t\ttcf_action_inc_drop_qstats(&c->common);\n\treturn TC_ACT_CONSUMED;\n\nTC_ACT_CONSUMED means the action took ownership of the skb, so no caller\nfrees it - sch_handle_ingress(), sch_handle_egress() and\ntcf_qevent_handle() all deliberately skip the free for that verdict. The\nskb is therefore orphaned: one sk_buff plus its data buffer is leaked per\nmalformed packet, unbounded. Note the drop counter is already incremented\nfor these errors, so the statistics claim a drop that never happens.\n\nThree different ownership states reach out_frag: today - the skb may be\nqueued by the defrag engine (-EINPROGRESS), already freed by\nnf_ct_handle_fragments(), or still owned by us. Tell the caller which of\nthose it is, and free the packet ourselves in the last case, which\nrestores the TC_ACT_SHOT behaviour that predated the Fixes: commit.\n\nReproduced on v7.2-rc6 with a 54-byte frame carrying a 40-byte IPv6\nheader with nexthdr = 0 (hop-by-hop) and nothing after it, on a\nclsact ingress chain with \"action ct\". kmemleak reports one leaked\n232-byte skbuff_head_cache object plus its 704-byte data buffer per\npacket; with this patch it reports none."
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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:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
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"baseScore": 7.5,
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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:N - The leak is triggered in tcf_ct_act() on the packet datapath (netif_receive_skb → sch_handle_ingress/egress → tc_run → tcf_classify); on OVN/Kubernetes/SDN gateways and mlx5-offload nodes with act_ct on clsact, a remote peer sends malformed IP packets with no local access required.\nAC:L - The attacker fully controls packet contents; a 54-byte IPv6 frame with nexthdr=0 (hop-by-hop) and no trailing data deterministically makes ipv6_find_hdr() return -EPROTO, leaking one skb per packet without races or uncontrollable layout dependencies.\nPR:N - Installing act_ct requires CAP_NET_ADMIN, but triggering the leak on an already-configured internet-facing or tenant-facing gateway needs no target credentials; a remote attacker only sends crafted malformed IP packets, matching CNA precedent for packet-driven act_ct issues (e.g., CVE-2026-72057).\nUI:N - Exploitation requires only attacker-generated malformed packets reaching a host with act_ct on clsact/ingress or egress; no victim login, mount, or other interactive action is needed beyond normal network traffic processing.\nS:U - The leaked sk_buff objects remain within the host kernel memory domain; this is not a VM escape, sandbox breakout, or IOMMU boundary bypass, only unbounded kernel heap consumption on the affected node.\nC:N - This is a pure sk_buff ownership leak on an error path; skb memory is orphaned, not exposed to the attacker, with no out-of-bounds read, use-after-free, or other disclosure primitive.\nI:N - The flaw only fails to kfree_skb() when header validation rejects a packet; it does not corrupt, overwrite, or modify any memory contents and provides no write or code-execution primitive.\nA:H - Each malformed packet leaks one sk_buff plus its data buffer (~936 bytes); sustained remote flooding causes unbounded kernel memory exhaustion and OOM denial of service, matching CNA precedent for repeatable network-triggered skb leaks (e.g., CVE-2026-52974)."
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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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"net/sched/act_ct.c"
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],
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"versions": [
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{
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"version": "172ba7d46c202e679f3ccb10264c67416aaeb1c4",
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"lessThan": "b5dbecc2016e1692fd1c2532af9c41ba729cb747",
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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": "0b5b831122fc3789fff75be433ba3e4dd7b779d4",
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"status": "affected",
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},
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"status": "affected",
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},
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"status": "affected",
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},
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{
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"lessThan": "b47bb899e04b5407c5a63fe88d4b6676586a6e84",
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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": "3f14b377d01d8357eba032b4cabc8c1149b458b6",
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"lessThan": "439d3e404f9d5e515911cc8132cde198b337c19e",
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"status": "affected",
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"status": "affected",
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},
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"version": "f5346df0591d10bc948761ca854b1fae6d2ef441",
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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": "5.15.148",
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"lessThan": "5.15.217",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "6.1.75",
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"lessThan": "6.1.184",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "6.6.14",
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"lessThan": "6.6.152",
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"status": "affected",
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"versionType": "semver"
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},
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{
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"version": "6.7.2",
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"lessThan": "6.8",
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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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"net/sched/act_ct.c"
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],
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"versions": [
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{
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"version": "6.8",
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"status": "affected"
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{
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"version": "0",
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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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},
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{
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},
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"version": "6.6.152",
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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": "6.12.104",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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},
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{
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"version": "6.18.45",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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},
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{
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"version": "7.1.9",
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"lessThanOrEqual": "7.1.*",
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"status": "unaffected",
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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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"cpeApplicability": [
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"references": [
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"url": "https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84"
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"url": "https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df"
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}
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],
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"title": "net/sched: act_ct: fix sk_buff leak when the header checks reject a packet",
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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-2026-74621",
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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": "yes"
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},
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{
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"Technical Impact": "partial"
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}
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],
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"version": "2.0.3",
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"timestamp": "2026-10-16T19:02:40.438798Z"
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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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"dateUpdated": "2026-10-16T19:06:02.607Z"
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}
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}
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]
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}
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} |