MediumFix available
unbound — security advisory
In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the 'dnscrypt:' clause lists more 'dnscrypt-provider-cert:' files than there are matching 'dnscrypt-secret-key:' files, Unbound fills only the matched prefix and leaves the tail slots at the '0xdb' fill that libsodium's allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with '0xdb' bytes. Any unauthenticated client that sends one UDP datagram of ≥ 68 bytes whose first 8 bytes are '0xdb' to 'dnscrypt-port' will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support ('--enable-dnscrypt').
- Products
- unbound
- Affected versions
- 1.17.1-2, 1.17.1-2+deb12u1, 1.17.1-2+deb12u2, 1.17.1-2+deb12u3, 1.17.1-2+deb12u4, 1.17.1-2+loong64, 1.18.0-1, 1.18.0-2, 1.19.1-1, 1.19.2-1, 1.20.0-1, 1.21.1-1, 1.22.0-1, 1.22.0-2, 1.22.0-2+deb13u1, 1.22.0-2+deb13u2, 1.22.0-2+deb13u3, 1.23.1-1, 1.24.0-1, 1.24.0-2, 1.24.1-1, 1.24.1-2, 1.24.2-1, 1.25.0-1, 1.25.1-1, 1.25.2-1, 1.26.0-1, 1.26.0-2, 1.26.1-1, 1.26.2-1
- Fixed versions
- 1.25.2-1, 1.26.1-0+deb13u1
- CVEs
- CVE-2026-55990
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 09:57 UTC · Revision 2
Source evidence
In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the 'dnscrypt:' clause lists more 'dnscrypt-provider-cert:' files than there are matching 'dnscrypt-secret-key:' files, Unbound fills only the matched prefix and leaves the tail slots at the '0xdb' fill that libsodium's allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with '0xdb' bytes. Any unauthenticated client that sends one UDP datagram of ≥ 68 bytes whose first 8 bytes are '0xdb' to 'dnscrypt-port' will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support ('--enable-dnscrypt').
osv:DEBIAN-CVE-2026-55990
unbound
Fixed versions: Not specified
unbound
Fixed versions: 1.26.1-0+deb13u1
unbound
Fixed versions: 1.25.2-1
Complete source record
{
"id": "846d191987adf391f1cb1804c5ad6b49ceffba69fdfa9796100205be02cfb624",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-55990",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-55990",
"summary": "In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the 'dnscrypt:' clause lists more 'dnscrypt-provider-cert:' files than there are matching 'dnscrypt-secret-key:' files, Unbound fills only the matched prefix and leaves the tail slots at the '0xdb' fill that libsodium's allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with '0xdb' bytes. Any unauthenticated client that sends one UDP datagram of ≥ 68 bytes whose first 8 bytes are '0xdb' to 'dnscrypt-port' will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support ('--enable-dnscrypt').",
"evidence": "osv:DEBIAN-CVE-2026-55990",
"products": [
{
"name": {
"value": "unbound",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.17.1-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.17.1-2+deb12u1",
"evidence": "/affected/0/versions"
},
{
"value": "1.17.1-2+deb12u2",
"evidence": "/affected/0/versions"
},
{
"value": "1.17.1-2+deb12u3",
"evidence": "/affected/0/versions"
},
{
"value": "1.17.1-2+deb12u4",
"evidence": "/affected/0/versions"
},
{
"value": "1.17.1-2+loong64",
"evidence": "/affected/0/versions"
},
{
"value": "1.18.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.18.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.20.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.21.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.22.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.22.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.23.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.24.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.24.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.24.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.24.1-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.24.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.25.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.25.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.25.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.26.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.26.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.26.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.26.2-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "unbound",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1.26.1-0+deb13u1",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": [
{
"value": "1.22.0-2",
"evidence": "/affected/1/versions"
},
{
"value": "1.22.0-2+deb13u1",
"evidence": "/affected/1/versions"
},
{
"value": "1.22.0-2+deb13u2",
"evidence": "/affected/1/versions"
},
{
"value": "1.22.0-2+deb13u3",
"evidence": "/affected/1/versions"
},
{
"value": "1.23.1-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.0-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.0-2",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.1-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.1-2",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.2-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.25.0-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.25.1-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.25.2-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.26.0-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.26.0-2",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "unbound",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1.25.2-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "1.22.0-2",
"evidence": "/affected/2/versions"
},
{
"value": "1.23.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.24.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.24.0-2",
"evidence": "/affected/2/versions"
},
{
"value": "1.24.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.24.1-2",
"evidence": "/affected/2/versions"
},
{
"value": "1.24.2-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.25.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.25.1-1",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "DEBIAN-CVE-2026-55990",
"aliases": [
"DEBIAN-CVE-2026-55990"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/debian/unbound?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"1.17.1-2",
"1.17.1-2+deb12u1",
"1.17.1-2+deb12u2",
"1.17.1-2+deb12u3",
"1.17.1-2+deb12u4",
"1.17.1-2+loong64",
"1.18.0-1",
"1.18.0-2",
"1.19.1-1",
"1.19.2-1",
"1.20.0-1",
"1.21.1-1",
"1.22.0-1",
"1.22.0-2",
"1.23.1-1",
"1.24.0-1",
"1.24.0-2",
"1.24.1-1",
"1.24.1-2",
"1.24.2-1",
"1.25.0-1",
"1.25.1-1",
"1.25.2-1",
"1.26.0-1",
"1.26.0-2",
"1.26.1-1",
"1.26.2-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55990.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.1-0+deb13u1"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/debian/unbound?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1.22.0-2",
"1.22.0-2+deb13u1",
"1.22.0-2+deb13u2",
"1.22.0-2+deb13u3",
"1.23.1-1",
"1.24.0-1",
"1.24.0-2",
"1.24.1-1",
"1.24.1-2",
"1.24.2-1",
"1.25.0-1",
"1.25.1-1",
"1.25.2-1",
"1.26.0-1",
"1.26.0-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55990.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.25.2-1"
}
]
}
],
"package": {
"name": "unbound",
"purl": "pkg:deb/debian/unbound?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"1.22.0-2",
"1.23.1-1",
"1.24.0-1",
"1.24.0-2",
"1.24.1-1",
"1.24.1-2",
"1.24.2-1",
"1.25.0-1",
"1.25.1-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55990.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-25T10:01:11.380792913Z",
"provider": "osv",
"upstream": [
"CVE-2026-55990"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-55990"
]
},
"related_cves": [
{
"value": "CVE-2026-55990",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 445387,
"published_at": "2026-07-22T14:17:21.81+00:00"
}