CVE-2026-42960

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A malicious actor can exploit the possible poisonous effect by injecting RRSets other than NS that are also accompanied by address records in a reply, for example MX. This could be achieved by trying to spoof a reply packet or fragmentation attacks. Unbound would then accept the relative address records in the additional section and cache them if the authority RRSet has enough trust at this point, i.e., in-zone data for the delegation point. Unbound 1.25.1 contains a patch with a fix that disregards address records from the additional section if they are not explicitly relevant only to authority NS records, mitigating the possible poison effect. This is a complement fix to CVE-2025-11411."}, {"lang": "es", "value": "NLnet Labs Unbound hasta e incluyendo la versi\u00f3n 1.25.0 es vulnerable a envenenamiento a trav\u00e9s de registros promiscuos para la secci\u00f3n de autoridad. Los RRSets promiscuos que complementan las respuestas DNS en la secci\u00f3n de autoridad pueden usarse para enga\u00f1ar a Unbound para que almacene en cach\u00e9 dichos registros. Si un adversario es capaz de adjuntar dichos registros en una respuesta (es decir, paquete falsificado, ataque de fragmentaci\u00f3n) podr\u00eda envenenar la cach\u00e9 de Unbound. Un actor malicioso puede exploit el posible efecto de envenenamiento inyectando RRSets distintos de NS que tambi\u00e9n est\u00e9n acompa\u00f1ados de registros de direcci\u00f3n en una respuesta, por ejemplo MX. Esto podr\u00eda lograrse intentando falsificar un paquete de respuesta o mediante ataques de fragmentaci\u00f3n. Unbound aceptar\u00eda entonces los registros de direcci\u00f3n relativos en la secci\u00f3n adicional y los almacenar\u00eda en cach\u00e9 si el RRSet de autoridad tiene suficiente confianza en este punto, es decir, datos en zona para el punto de delegaci\u00f3n. Unbound 1.25.1 contiene un parche con una correcci\u00f3n que ignora los registros de direcci\u00f3n de la secci\u00f3n adicional si no son expl\u00edcitamente relevantes solo para los registros NS de autoridad, mitigando el posible efecto de envenenamiento. Esta es una correcci\u00f3n complementaria a CVE-2025-11411."}], "id": "CVE-2026-42960", "lastModified": "2026-07-24T10:10:00.197", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 10.0, "baseSeverity": "CRITICAL", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.8, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "ADJACENT", "availabilityRequirement": "NOT_DEFINED", "baseScore": 5.7, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "PROOF_OF_CONCEPT", "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": "AMBER", "subAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "HIGH", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:H/E:P/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:Amber", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "sep@nlnetlabs.nl", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-42960", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-05-20T13:04:22.642063Z", "version": "2.0.3"}}]}, "published": "2026-05-20T10:16:28.037", "references": [{"source": "sep@nlnetlabs.nl", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42960.txt"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-349"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}

{"acknowledgement": "Red Hat would like to thank JianJun Chen (Tsinghua University), TaoFei Guo (Peking University), and Yang Luo (Tsinghua University) for reporting this issue.", "bugzilla": {"description": "unbound: Unbound DNS Cache Poisoning via Promiscuous Additional Section RRSet Acceptance", "id": "2479821", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2479821"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.9", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N", "status": "draft"}, "cwe": "CWE-349", "details": ["A flaw was found in Unbound's handling of DNS reply messages, complementing the earlier CVE-2025-11411 fix. Unbound accepts and caches address records from the additional section of DNS replies when they accompany authority section RRSets other than NS (such as MX records). A malicious actor who can inject crafted DNS responses\u2014via packet spoofing or fragmentation attacks\u2014can exploit this to poison Unbound's cache with attacker-controlled address records, potentially redirecting DNS resolution for affected domains."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-42960", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "unbound", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Fix deferred", "package_name": "unbound", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "unbound", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "unbound", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "unbound", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Affected", "package_name": "unbound", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "rhcos", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-05-20T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-42960\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-42960"], "statement": "The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate. Exploitation requires the attacker to successfully inject or spoof DNS response packets, which increases attack complexity. However, successful exploitation can result in DNS cache poisoning, allowing the attacker to redirect DNS resolution for affected domains.", "threat_severity": "Moderate"}

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