{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-81634", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "state": "PUBLISHED", "assignerShortName": "NLnet Labs", "dateReserved": "2026-09-07T14:06:21.967Z", "datePublished": "2026-09-16T08:30:15.428Z", "dateUpdated": "2026-09-16T08:30:15.428Z"}, "containers": {"cna": {"title": "Possible heap buffer overflow during DNSSEC canonicalization", "datePublic": "2026-09-16T00:00:00.000Z", "affected": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"version": "0", "status": "affected", "lessThan": "1.26.1", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability."}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "baseScore": 7.5, "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}}], "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-122", "description": "CWE-122: Heap-based Buffer Overflow", "type": "CWE"}]}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.26.1"}], "timeline": [{"time": "2026-07-31T00:00:00.000Z", "lang": "en", "value": "Issue reported by Vlatko Kosturjak"}, {"time": "2026-08-03T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch"}, {"time": "2026-08-04T00:00:00.000Z", "lang": "en", "value": "Vlatko Kosturjak verifies patch"}, {"time": "2026-09-16T00:00:00.000Z", "lang": "en", "value": "Fixes released with version 1.26.1"}], "credits": [{"lang": "en", "value": "Vlatko Kosturjak (Marlink Cyber)", "type": "finder"}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt", "tags": ["vendor-advisory"]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-09-16T08:30:15.428Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Unbound", "vendor": "NLnet Labs", "versions": [{"lessThan": "1.26.1", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "sep@nlnetlabs.nl"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound up to and including 1.26.0, a 255 length query name with a large TCP response can lead to a heap buffer overflow during the RRSet canonicalisation routine. This is caused by missing to add the first owner name into the buffer length check. A malicious actor operating a malicious name server or tampering with an incoming response to Unbound (canonicalisation happens before DNSSEC validation), can trigger the vulnerability."}], "id": "CVE-2026-81634", "lastModified": "2026-09-16T09:17:06.210", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}, "published": "2026-09-16T09:17:06.210", "references": [{"source": "sep@nlnetlabs.nl", "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-81634.txt"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-122"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}

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