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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": "openshift/ose-rhel-coreos-9", "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. This may cause crashes and could potentially allow arbitrary code execution." } ], "metrics": [ { "other": { "content": { "namespace": "https://access.redhat.com/security/updates/classification/", "value": "Important" }, "type": "Red Hat severity rating" } }, { "cvssV3_1": { "attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 8.1, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1" }, "format": "CVSS" } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-416", "description": "Use After Free", "lang": "en", "type": "CWE" } ] } ], "references": [ { "tags": [ "vdb-entry", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/security/cve/CVE-2026-33278" }, { "name": "RHBZ#2479808", "tags": [ "issue-tracking", "x_refsource_REDHAT" ], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2479808" }, { "tags": [ "x_sadp-csaf-vex" ], "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33278.json" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:23231" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:24369" }, { "tags": [ "vendor-advisory", "x_refsource_REDHAT" ], "url": "https://access.redhat.com/errata/RHSA-2026:19752" } ], "solutions": [ { "lang": "en", "value": "RHSA-2026:23231: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)" }, { "lang": "en", "value": "RHSA-2026:24369: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)" }, { "lang": "en", "value": "RHSA-2026:19752: Red Hat Hardened Images" } ], "timeline": [ { "lang": "en", "time": "2026-05-19T11:46:56.937Z", "value": "Reported to Red Hat." }, { "lang": "en", "time": "2026-05-20T11:33:59.504Z", "value": "Made public." } ], "title": "unbound: Unbound DNSSEC Validator Use-After-Free via Deep Copy Pointer Overwrite Leading to DoS and Possible Remote Code Execution", "x_adpType": "supplier", "x_generator": { "engine": "sadp-cli 1.0.0" }, "providerMetadata": { "orgId": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "shortName": "redhat-SADP", "dateUpdated": "2026-09-01T12:04:59.092Z" } } ] } }