CVE-2026-33278

NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.

References

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt

Affected packages

Git / github.com/nlnetlabs/unbound

Affected ranges

Type

GIT

Repo

https://github.com/nlnetlabs/unbound

Events

Introduced

c6dd1e116df75242a0c032295c152f06c721b3cd

Fixed

75b6dba593d4fff000434cd64807c6ebd50bd244

Database specific

{
    "extracted_events": [
        {
            "introduced": "1.19.1"
        },
        {
            "fixed": "1.25.1"
        }
    ],
    "cpe": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*",
    "source": "CPE_RANGE"
}

Database specific

vanir_signatures

[
    {
        "digest": {
            "length": 1502.0,
            "function_hash": "26148135886169857913239956572075736548"
        },
        "signature_version": "v1",
        "id": "CVE-2026-33278-7cb89fac",
        "target": {
            "file": "services/rpz.c",
            "function": "rpz_callback_from_iterator_module"
        },
        "deprecated": false,
        "source": "https://github.com/nlnetlabs/unbound/commit/75b6dba593d4fff000434cd64807c6ebd50bd244",
        "signature_type": "Function"
    },
    {
        "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
        },
        "id": "CVE-2026-33278-a3b17d2e",
        "signature_version": "v1",
        "target": {
            "file": "services/rpz.c"
        },
        "deprecated": false,
        "signature_type": "Line",
        "source": "https://github.com/nlnetlabs/unbound/commit/75b6dba593d4fff000434cd64807c6ebd50bd244"
    }
]

vanir_signatures_modified

"2026-05-31T03:35:25Z"

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-33278.json"