271 lines
14 KiB
JSON
271 lines
14 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-2021-47555",
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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": "2024-05-24T15:02:54.833Z",
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"datePublished": "2024-05-24T15:09:57.302Z",
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"dateUpdated": "2026-08-05T08:48:23.118Z"
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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": "2026-08-05T08:48:23.118Z"
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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: vlan: fix underflow for the real_dev refcnt\n\nInject error before dev_hold(real_dev) in register_vlan_dev(),\nand execute the following testcase:\n\nip link add dev dummy1 type dummy\nip link add name dummy1.100 link dummy1 type vlan id 100\nip link del dev dummy1\n\nWhen the dummy netdevice is removed, we will get a WARNING as following:\n\n=======================================================================\nrefcount_t: decrement hit 0; leaking memory.\nWARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0\n\nand an endless loop of:\n\n=======================================================================\nunregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824\n\nThat is because dev_put(real_dev) in vlan_dev_free() be called without\ndev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev\nunderflow.\n\nMove the dev_hold(real_dev) to vlan_dev_init() which is the call-back of\nndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev\nsymmetrical."
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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 - The bug is reached only through local RTNL/ioctl VLAN creation (RTM_NEWLINK → vlan_newlink → register_vlan_dev, or ADD_VLAN_CMD), not via received packets or a remote protocol handler.\nAC:L - An attacker can reliably force the vulnerable error path after register_netdevice()/ndo_init by making netdev_upper_dev_link() fail (e.g. nesting past MAX_NEST_DEV=8), so vlan_dev_free() runs dev_put(real_dev) without a matching hold.\nPR:L - Creating VLAN devices requires CAP_NET_ADMIN checked with netlink_ns_capable()/ns_capable() against the netns user_ns, which an unprivileged user can obtain via user namespaces (unshare -Urn) with dummy/veth+vlan inside the new netns.\nUI:N - The attacker creates and tears down their own netdevices to trigger the underflow; no separate victim action is required.\nS:U - Impact is confined to the local host kernel (netdev refcnt underflow/UAF/DoS) and does not cross a VM, IOMMU, or other security-authority boundary.\nC:H - The extra dev_put() undercounts real_dev; when the displayed refcnt hits 1 while another holder still exists, wait_allrefs can free the net_device early (UAF), enabling heap reuse and kernel memory disclosure via netdev_ops/adjacent state.\nI:H - A use-after-free of struct net_device is exploitable for heap corruption and control-flow hijack (function pointers in netdev_ops and related objects), matching UAF integrity guidance.\nA:H - The demonstrated impact is refcount saturation/underflow leading to an endless unregister_netdevice wait (Usage count stuck) or a kernel oops on UAF, either of which is a full availability loss."
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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/8021q/vlan.c",
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"net/8021q/vlan_dev.c"
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],
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"versions": [
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{
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"version": "700602b662d7eaa816b1a3cb0abe7a85de358fd4",
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"lessThan": "5e44178864b38dd70b877985abd7d86fdb95f27d",
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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": "e04a7a84bb77f9cdf4475340fe931389bc72331c",
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"lessThan": "6e800ee43218a56acc93676bbb3d93b74779e555",
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"status": "affected",
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"lessThan": "f7fc72a508cf115c273a7a29350069def1041890",
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"status": "affected",
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"version": "563bcbae3ba233c275c244bfce2efe12938f5363",
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"lessThan": "01d9cc2dea3fde3bad6d27f464eff463496e2b00",
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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": "fca96b3f852a1b369b7b2844ce357cd689879934",
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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": "5.14.19",
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"lessThan": "5.15",
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"status": "affected",
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"versionType": "semver"
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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": "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/8021q/vlan.c",
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"net/8021q/vlan_dev.c"
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],
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"versions": [
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{
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"version": "5.4.160",
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"lessThan": "5.4.163",
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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": "5.10.80",
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"lessThan": "5.10.83",
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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": "5.15.3",
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"lessThan": "5.15.6",
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"status": "affected",
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"versionType": "semver"
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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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"cpeMatch": [
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionEndExcluding": "5.4.163"
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "5.15.3",
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/5e44178864b38dd70b877985abd7d86fdb95f27d"
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},
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{
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"url": "https://git.kernel.org/stable/c/6e800ee43218a56acc93676bbb3d93b74779e555"
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},
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{
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"url": "https://git.kernel.org/stable/c/f7fc72a508cf115c273a7a29350069def1041890"
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},
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{
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"url": "https://git.kernel.org/stable/c/01d9cc2dea3fde3bad6d27f464eff463496e2b00"
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}
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],
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"title": "net: vlan: fix underflow for the real_dev refcnt",
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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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{
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"descriptions": [
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{
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"type": "CWE",
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"lang": "en",
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"description": "CWE-noinfo Not enough information"
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}
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]
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}
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],
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"metrics": [
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{
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"scope": "UNCHANGED",
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"version": "3.1",
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"baseScore": 4.4,
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"attackVector": "LOCAL",
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"baseSeverity": "MEDIUM",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L",
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"integrityImpact": "NONE",
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"userInteraction": "NONE",
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"attackComplexity": "LOW",
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"availabilityImpact": "LOW",
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"privilegesRequired": "LOW",
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"confidentialityImpact": "LOW"
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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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"timestamp": "2024-05-29T16:50:13.639283Z",
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"id": "CVE-2021-47555",
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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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"Technical Impact": "partial"
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"role": "CISA Coordinator",
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"version": "2.0.3"
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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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"shortName": "CISA-ADP",
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"dateUpdated": "2024-11-04T20:18:51.592Z"
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"dateUpdated": "2024-08-04T05:39:59.857Z"
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"title": "CVE Program Container",
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"references": [
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