Heap overflow with multiple NSID, COOKIE, PADDING EDNS options_CVE-2026-42944

{
    "lastseen": "",
    "description": "NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.",
    "published": "2026-05-20T09:20:23.906Z",
    "modified": "2026-05-20T09:20:23.906Z",
    "type": "cve",
    "title": "Heap overflow with multiple NSID, COOKIE, PADDING EDNS options",
    "source": "NLnet Labs",
    "references": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42944.txt",
    "id": "CVE-2026-42944",
    "bulletinFamily": "",
    "cwe": [
        "CWE-197",
        "CWE-787"
    ],
    "cvelist": null,
    "sourceData": "NLnet Labs Unbound 1.14.0",
    "sourceHref": "",
    "cvss": {
        "score": 8.7,
        "severity": "HIGH",
        "vector": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Red",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Unbound",
    "version": "1.14.0",
    "vendor": "NLnet Labs",
    "ai_description": "Heap overflow vulnerability in Unbound when encoding multiple NSID, COOKIE, and PADDING EDNS options",
    "ai_severity": "High",
    "ai_vendor": "NLnet Labs",
    "ai_product": "Unbound",
    "ai_version": "1.14.0-1.25.0",
    "ai_score": 8.7
}