CVE-2026-40622

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.

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-40622.txt

Affected packages

Git / github.com/nlnetlabs/unbound

Affected ranges

Type

GIT

Repo

https://github.com/nlnetlabs/unbound

Events

Introduced

cbed768b8ff9bfcf11089a5f1699b7e5707f1ea5

Fixed

75b6dba593d4fff000434cd64807c6ebd50bd244

Database specific

{
    "extracted_events": [
        {
            "introduced": "1.16.2"
        },
        {
            "fixed": "1.25.1"
        }
    ],
    "cpe": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
    "source": "CPE_RANGE"
}

Affected versions

release-1.*

release-1.16.2

release-1.18.0

release-1.18.0rc1

release-1.19.0

release-1.19.0rc1

release-1.19.3rc1

release-1.20.0

release-1.20.0rc1

release-1.21.0

release-1.21.0rc1

release-1.22.0

release-1.22.0rc1

release-1.23.0rc1

release-1.24.0

release-1.24.0rc1

release-1.25.0

release-1.25.0rc1

Database specific

vanir_signatures

[
    {
        "digest": {
            "function_hash": "26148135886169857913239956572075736548",
            "length": 1502.0
        },
        "id": "CVE-2026-40622-7cb89fac",
        "signature_version": "v1",
        "target": {
            "file": "services/rpz.c",
            "function": "rpz_callback_from_iterator_module"
        },
        "deprecated": false,
        "signature_type": "Function",
        "source": "https://github.com/nlnetlabs/unbound/commit/75b6dba593d4fff000434cd64807c6ebd50bd244"
    },
    {
        "digest": {
            "line_hashes": [
                "108481287081154918060659085654141150584",
                "73953166938600086918224773195867549742",
                "15251087855327528788980657535362970158",
                "48532896601082718174781974683716349061",
                "287248990686482337183326495344180868363",
                "112058947495561481565691171486557666856",
                "238258467286774268681997190612827183971",
                "126648031849056156900266153546629664662",
                "335401097143186200364020904286165936708",
                "336096779053276656395004922884987906159",
                "248876396313049466881138460638611830858",
                "293135123655960925553682804594622081358",
                "298612071867479354827766089224387452786",
                "217265304546593372824910550975155656654",
                "13292601781282786772501437491204364169",
                "281286782737850123600796590480125479595",
                "74511316679551775089931390035715335201",
                "161066344018382590627892027575409612852",
                "226343512543910522766563315515650712879"
            ],
            "threshold": 0.9
        },
        "signature_version": "v1",
        "id": "CVE-2026-40622-a3b17d2e",
        "target": {
            "file": "services/rpz.c"
        },
        "deprecated": false,
        "signature_type": "Line",
        "source": "https://github.com/nlnetlabs/unbound/commit/75b6dba593d4fff000434cd64807c6ebd50bd244"
    }
]

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-40622.json"

vanir_signatures_modified

"2026-05-31T03:35:34Z"