HighFix available
unbound — security advisory
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.
- Products
- unbound
- Affected versions
- 1.17.1-2, 1.18.0-2ubuntu1, 1.18.0-2ubuntu2, 1.19.1-1ubuntu1, 1.19.2-1ubuntu1, 1.19.2-1ubuntu3, 1.19.2-1ubuntu3.1, 1.19.2-1ubuntu3.2, 1.19.2-1ubuntu3.3, 1.19.2-1ubuntu3.4, 1.19.2-1ubuntu3.5, 1.19.2-1ubuntu3.6, 1.19.2-1ubuntu3.7, 1.22.0-1ubuntu1, 1.22.0-2ubuntu1, 1.22.0-2ubuntu2, 1.22.0-2ubuntu2.1, 1.22.0-2ubuntu2.2, 1.22.0-2ubuntu4, 1.24.2-1ubuntu1, 1.24.2-1ubuntu2, 1.4.22-1ubuntu6, 1.5.7-1ubuntu1, 1.5.7-1ubuntu2, 1.5.8-1ubuntu1, 1.5.8-1ubuntu1.1, 1.5.8-1ubuntu1.1+esm1, 1.5.8-1ubuntu1.1+esm2, 1.5.8-1ubuntu1.1+esm3, 1.5.8-1ubuntu1.1+esm4, 1.5.8-1ubuntu1.1+esm5
- Fixed versions
- 1.19.2-1ubuntu3.8, 1.22.0-2ubuntu2.3, 1.24.2-1ubuntu2.1
- CVEs
- CVE-2026-40622
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 14:34 UTC · Revision 1
Source evidence
NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.
osv:UBUNTU-CVE-2026-40622
unbound
Fixed versions: Not specified
unbound
Fixed versions: 1.19.2-1ubuntu3.8
unbound
Fixed versions: 1.22.0-2ubuntu2.3
unbound
Fixed versions: 1.24.2-1ubuntu2.1
Complete source record
{
"id": "67926fdb04fb9eae00bfd5fca93764e39ac12e3464f228234283e26ded84de22",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-40622",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-40622",
"summary": "NLnet Labs Unbound 1.16.2 up to and including version 1.25.0 has a vulnerability of the 'ghost domain names' family of attacks that could extend the ghost domain window by up to one cached TTL configured value. Similar to other 'ghost domain names' attacks, an adversary needs to control a (ghost) zone and be able to query a vulnerable Unbound. A single client NS query can cause Unbound to overwrite the cached expired parent-side referral NS rrset with the child-side apex NS rrset and essentially extend the ghost domain window by up to one cached TTL configured value ('cache-max-ttl'). In configurations where 'harden-referral-path: yes' is used (non-default configuration), no client NS query is required since Unbound implicitly performs that query. Unbound 1.25.1 contains a patch with a fix that does not allow extension of TTLs for (parent) NS records regardless of their trust.",
"evidence": "osv:UBUNTU-CVE-2026-40622",
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{
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{
"name": {
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{
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"evidence": "/affected/2/versions"
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{
"value": "1.22.0-2ubuntu1",
"evidence": "/affected/2/versions"
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{
"value": "1.22.0-2ubuntu2",
"evidence": "/affected/2/versions"
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{
"value": "1.22.0-2ubuntu2.1",
"evidence": "/affected/2/versions"
},
{
"value": "1.22.0-2ubuntu2.2",
"evidence": "/affected/2/versions"
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},
{
"name": {
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"evidence": "/affected/3/package/name"
},
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{
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"evidence": "/affected/3/ranges"
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],
"affected_versions": [
{
"value": "1.22.0-2ubuntu2",
"evidence": "/affected/3/versions"
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{
"value": "1.22.0-2ubuntu4",
"evidence": "/affected/3/versions"
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{
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"evidence": "/affected/3/versions"
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{
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"evidence": "/affected/3/versions"
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}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2026-40622",
"aliases": [
"UBUNTU-CVE-2026-40622"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/ubuntu/unbound?arch=source&distro=esm-infra-legacy%2Fxenial",
"ecosystem": "Ubuntu:Pro:16.04:LTS"
},
"versions": [
"1.4.22-1ubuntu6",
"1.5.7-1ubuntu1",
"1.5.7-1ubuntu2",
"1.5.8-1ubuntu1",
"1.5.8-1ubuntu1.1",
"1.5.8-1ubuntu1.1+esm1",
"1.5.8-1ubuntu1.1+esm2",
"1.5.8-1ubuntu1.1+esm3",
"1.5.8-1ubuntu1.1+esm4",
"1.5.8-1ubuntu1.1+esm5"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40622.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libunbound2",
"binary_version": "1.5.8-1ubuntu1.1+esm5"
},
{
"binary_name": "python-unbound",
"binary_version": "1.5.8-1ubuntu1.1+esm5"
},
{
"binary_name": "unbound",
"binary_version": "1.5.8-1ubuntu1.1+esm5"
},
{
"binary_name": "unbound-anchor",
"binary_version": "1.5.8-1ubuntu1.1+esm5"
},
{
"binary_name": "unbound-host",
"binary_version": "1.5.8-1ubuntu1.1+esm5"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
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{
"fixed": "1.19.2-1ubuntu3.8"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/ubuntu/unbound?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"1.17.1-2",
"1.18.0-2ubuntu1",
"1.18.0-2ubuntu2",
"1.19.1-1ubuntu1",
"1.19.2-1ubuntu1",
"1.19.2-1ubuntu3",
"1.19.2-1ubuntu3.1",
"1.19.2-1ubuntu3.2",
"1.19.2-1ubuntu3.3",
"1.19.2-1ubuntu3.4",
"1.19.2-1ubuntu3.5",
"1.19.2-1ubuntu3.6",
"1.19.2-1ubuntu3.7"
],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libunbound8",
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{
"binary_name": "python3-unbound",
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},
{
"binary_name": "unbound",
"binary_version": "1.19.2-1ubuntu3.8"
},
{
"binary_name": "unbound-anchor",
"binary_version": "1.19.2-1ubuntu3.8"
},
{
"binary_name": "unbound-host",
"binary_version": "1.19.2-1ubuntu3.8"
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],
"availability": "No subscription required"
}
},
{
"ranges": [
{
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"package": {
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{
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{
"binary_name": "unbound-anchor",
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},
{
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"versions": [
"1.22.0-2ubuntu2",
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{
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{
"binary_name": "unbound-anchor",
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},
{
"binary_name": "unbound-host",
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],
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}
}
],
"modified": "2026-10-21T16:30:58.339106229Z",
"provider": "osv",
"upstream": [
"CVE-2026-40622"
],
"references": [
"https://ubuntu.com/security/CVE-2026-40622",
"https://www.cve.org/CVERecord?id=CVE-2026-40622",
"https://nlnetlabs.nl/news/2026/May/20/unbound-1.25.1-released/",
"https://ubuntu.com/security/notices/USN-8282-1"
]
},
"related_cves": [
{
"value": "CVE-2026-40622",
"evidence": "/upstream"
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],
"security_relevant": true,
"severity_evidence": "/severity/1/score"
},
"source_id": "core-osv",
"document_id": 394525,
"published_at": "2026-05-20T00:00:00+00:00"
}