{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-85501", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "state": "PUBLISHED", "assignerShortName": "NLnet Labs", "dateReserved": "2026-09-07T14:06:21.977Z", "datePublished": "2026-09-16T08:32:25.398Z", "dateUpdated": "2026-09-16T14:12:18.996Z"}, "containers": {"cna": {"title": "Retrap: Novel Vulnerabilities to launch Algorithmic Complexity Attacks on DNSSEC", "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": "Novel vulnerabilities to launch algorithmic complexity attacks on DNSSEC have been researched under the term 'ReTrap'. These result in degradation of service when malicious zones are used to serve the algorithmic complexity vulnerabilities. NLnet Labs Unbound up to and including 1.26.0 is vulnerable to some of them. TagTrap, where the triple(Zone, Algo, KeyTag) matching mechanism introduces a significant attack vector when resolvers handle malicious responses containing numerous mismatched DNSKEY, RRSIG, and DS record. DelegationTrap, where constructing the chain-of-trust requires iterative validation of DNSKEY and DS records from the root zone downward. For deeply nested domains, this results in significant computational overhead. NsecTrap, where responses with excessive invalid NSEC records compel the resolver to validate each one. AdditionalTrap, where Unbound by default would try to DNSSEC validate the ADDITIONAL section as well. This can be exploited to waste validation resources by malicious users."}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV3_1": {"version": "3.1", "baseScore": 5.3, "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}}], "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-770", "description": "CWE-770: Allocation of Resources Without Limits or Throttling", "type": "CWE"}]}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.26.1"}], "timeline": [{"time": "2025-05-24T00:00:00.000Z", "lang": "en", "value": "Issue reported by Zuyao Xu"}, {"time": "2025-05-28T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares some concerns about the testing methodology"}, {"time": "2025-08-14T00:00:00.000Z", "lang": "en", "value": "Zuyao Xu shares updated research results"}, {"time": "2025-08-26T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch with Zuyao Xu"}, {"time": "2025-09-03T00:00:00.000Z", "lang": "en", "value": "Zuyao Xu verifies patch"}, {"time": "2026-05-05T00:00:00.000Z", "lang": "en", "value": "Issue similar to TagTrap reported by Qifan Zhang"}, {"time": "2026-05-07T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch with Qifan Zhang"}, {"time": "2026-05-08T00:00:00.000Z", "lang": "en", "value": "Qifan Zhang verifies patch"}, {"time": "2026-09-16T00:00:00.000Z", "lang": "en", "value": "Fixes released with version 1.26.1"}], "credits": [{"lang": "en", "value": "Zuyao Xu (Nankai University, AOSP Lab)", "type": "finder"}, {"lang": "en", "value": "Xiang Li (Nankai University, AOSP Lab)", "type": "finder"}, {"lang": "en", "value": "Qifan Zhang (Palo Alto Networks)", "type": "finder"}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt", "tags": ["vendor-advisory"]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-09-16T08:32:25.398Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-09-16T14:10:48.623819Z", "id": "CVE-2026-85501", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-09-16T14:12:18.996Z"}}]}}

{}

{"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": "Novel vulnerabilities to launch algorithmic complexity attacks on DNSSEC have been researched under the term 'ReTrap'. These result in degradation of service when malicious zones are used to serve the algorithmic complexity vulnerabilities. NLnet Labs Unbound up to and including 1.26.0 is vulnerable to some of them. TagTrap, where the triple(Zone, Algo, KeyTag) matching mechanism introduces a significant attack vector when resolvers handle malicious responses containing numerous mismatched DNSKEY, RRSIG, and DS record. DelegationTrap, where constructing the chain-of-trust requires iterative validation of DNSKEY and DS records from the root zone downward. For deeply nested domains, this results in significant computational overhead. NsecTrap, where responses with excessive invalid NSEC records compel the resolver to validate each one. AdditionalTrap, where Unbound by default would try to DNSSEC validate the ADDITIONAL section as well. This can be exploited to waste validation resources by malicious users."}], "id": "CVE-2026-85501", "lastModified": "2026-09-16T09:17:06.783", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 5.3, "baseSeverity": "MEDIUM", "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:L", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}, "published": "2026-09-16T09:17:06.783", "references": [{"source": "sep@nlnetlabs.nl", "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-770"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}

{"bugzilla": {"description": "unbound: Unbound: Denial of Service via algorithmic complexity attacks on DNSSEC", "id": "2535057", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2535057"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-770", "details": ["A flaw was found in Unbound. This vulnerability, termed 'ReTrap', allows a remote attacker to launch algorithmic complexity attacks on the Domain Name System Security Extensions (DNSSEC) validation process. By serving malicious zones or responses, an attacker can exploit various mechanisms, such as mismatched DNSKEY records, deeply nested domains, or excessive invalid NSEC records. Successful exploitation leads to a degradation of service, effectively causing a Denial of Service (DoS) for affected Unbound resolvers."], "name": "CVE-2026-85501", "package_state": [{"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift/ose-rhel-coreos-8", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "openshift/ose-rhel-coreos-9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-09-16T08:32:25Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-85501\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-85501\nhttps://www.nlnetlabs.nl/downloads/unbound/CVE-2026-85501.txt"], "threat_severity": "Moderate"}

{"created": "2026-09-16T14:00:11.969880+00:00", "updated": "2026-09-16T14:00:11.969890+00:00", "vendors": []}