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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" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-05-20T12:13:01.681597Z", "id": "CVE-2026-33278", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "total" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-20T12:13:09.692Z" } }, { "affected": [ { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/o:redhat:enterprise_linux:10.2" ], "defaultStatus": "affected", "packageName": "unbound", "product": "Red Hat Enterprise Linux 10", "vendor": "Red Hat", "versions": [ { "lessThan": "*", "status": "unaffected", "version": "0:1.24.2-7.el10_2.1", "versionType": "rpm" } ] }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:enterprise_linux:9" ], "defaultStatus": "affected", "packageName": "unbound", "product": "Red Hat Enterprise Linux 9", "vendor": "Red Hat", "versions": [ { "lessThan": "*", "status": "unaffected", "version": "0:1.24.2-3.el9_8.1", "versionType": "rpm" } ] }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:hummingbird:1" ], "defaultStatus": "affected", "packageName": "unbound-main", "product": "Red Hat Hardened Images", "vendor": "Red Hat", "versions": [ { "lessThan": "*", "status": "unaffected", "version": "1.25.1-0.1.hum1", "versionType": "rpm" } ] }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/o:redhat:enterprise_linux:6" ], "defaultStatus": "unknown", "packageName": "unbound", "product": "Red Hat Enterprise Linux 6", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/o:redhat:enterprise_linux:7" ], "defaultStatus": "unaffected", "packageName": "unbound", "product": "Red Hat Enterprise Linux 7", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/o:redhat:enterprise_linux:8" ], "defaultStatus": "unaffected", "packageName": "unbound", "product": "Red Hat Enterprise Linux 8", "vendor": "Red Hat" }, { "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "cpes": [ "cpe:/a:redhat:openshift:4" ], "defaultStatus": "affected", "packageName": "rhcos", "product": "Red Hat OpenShift Container Platform 4", "vendor": "Red Hat" } ], "datePublic": "2026-05-20T11:33:59.504Z", "descriptions": [ { "lang": "en", "value": "A flaw was discovered in Unbound’s DNSSEC validator can leave it using an invalid memory pointer after certain DS sub-query validations fail due to NSEC3 budget exhaustion. 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