{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-33278", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "state": "PUBLISHED", "assignerShortName": "NLnet Labs", "dateReserved": "2026-05-07T10:07:51.853Z", "datePublished": "2026-05-20T09:18:15.225Z", "dateUpdated": "2026-05-20T09:18:15.225Z"}, "containers": {"cna": {"title": "Possible arbitrary code execution during DNSSEC validation", "datePublic": "2026-05-20T00:00:00.000Z", "affected": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"version": "1.19.1", "status": "affected", "lessThan": "1.25.1", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "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."}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"version": "4.0", "baseScore": 9.1, "baseSeverity": "CRITICAL", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red"}}], "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-416", "description": "CWE-416: Use After Free", "type": "CWE"}, {"lang": "en", "cweId": "CWE-672", "description": "CWE-672: Operation on a Resource after Expiration or Release", "type": "CWE"}]}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.25.1"}], "timeline": [{"time": "2026-04-15T00:00:00.000Z", "lang": "en", "value": "Issue reported by Qifan Zhang"}, {"time": "2026-04-29T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch"}, {"time": "2026-04-29T00:00:00.000Z", "lang": "en", "value": "Qifan Zhang verifies patch"}, {"time": "2026-05-20T00:00:00.000Z", "lang": "en", "value": "Fixes released with version 1.25.1"}], "credits": [{"lang": "en", "value": "Qifan Zhang (Palo Alto Networks)", "type": "finder"}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt", "tags": ["vendor-advisory"]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-05-20T09:18:15.225Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

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{"cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-33278", "lastModified": "2026-05-20T10:16:26.530", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "UNREPORTED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "RED", "subAvailabilityImpact": "HIGH", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Red", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}, "published": "2026-05-20T10:16:26.530", "references": [{"source": "sep@nlnetlabs.nl", "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-33278.txt"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}, {"lang": "en", "value": "CWE-672"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}

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{"created": "2026-05-20T11:30:26.140242+00:00", "updated": "2026-05-20T11:30:26.140252+00:00", "vendors": []}