CVE-2026-42534

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Retransmits of the same query could renew the age of slow running queries and not allow the jostle logic to see them as aged and potential targets for replacement with new queries. An adversary who can query a vulnerable Unbound and who can control a domain name server that replies slowly and/or maliciously to Unbound's queries can exploit the vulnerability and degrade the resolution performance of Unbound. When Unbound's 'num-queries-per-thread' reaches its limit, the jostle logic kicks in. When a new query comes in, half of the available queries that are also slow to resolve are candidates for replacement. The vulnerability then happens because duplicate queries that need resolution would skew the aging result by using the timestamp of the latest duplicate query instead of the original one that started the resolution effort. Cache and local data response performance remains unaffected. Coordinated attacks could raise this to a denial of resolution service. Unbound 1.25.1 contains a patch with a fix to attach an initial, non-updatable start time for incoming queries that allow the jostle logic to work as intended."}, {"lang": "es", "value": "NLnet Labs Unbound hasta e incluyendo la versi\u00f3n 1.25.0 tiene una vulnerabilidad en la l\u00f3gica de jostle que podr\u00eda anular su prop\u00f3sito y degradar el rendimiento de la resoluci\u00f3n. Las retransmisiones de la misma consulta podr\u00edan renovar la antig\u00fcedad de las consultas de ejecuci\u00f3n lenta y no permitir que la l\u00f3gica de jostle las vea como antiguas y posibles objetivos para ser reemplazadas por nuevas consultas. Un adversario que puede consultar un Unbound vulnerable y que puede controlar un servidor de nombres de dominio que responde lenta y/o maliciosamente a las consultas de Unbound puede explotar la vulnerabilidad y degradar el rendimiento de la resoluci\u00f3n de Unbound. Cuando 'num-queries-per-thread' de Unbound alcanza su l\u00edmite, la l\u00f3gica de jostle se activa. Cuando llega una nueva consulta, la mitad de las consultas disponibles que tambi\u00e9n son lentas de resolver son candidatas para ser reemplazadas. La vulnerabilidad ocurre entonces porque las consultas duplicadas que necesitan resoluci\u00f3n sesgar\u00edan el resultado de la antig\u00fcedad al usar la marca de tiempo de la \u00faltima consulta duplicada en lugar de la original que inici\u00f3 el esfuerzo de resoluci\u00f3n. El rendimiento de la respuesta de la cach\u00e9 y los datos locales permanece inalterado. Ataques coordinados podr\u00edan elevar esto a una denegaci\u00f3n de servicio de resoluci\u00f3n. Unbound 1.25.1 contiene un parche con una correcci\u00f3n para adjuntar un tiempo de inicio inicial no actualizable para las consultas entrantes que permite que la l\u00f3gica de jostle funcione seg\u00fan lo previsto."}], "id": "CVE-2026-42534", "lastModified": "2026-09-01T13:19:28.690", "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": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "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:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "type": "Secondary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.9, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "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": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/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": "LOW", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "sep@nlnetlabs.nl", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-42534", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-05-20T12:10:33.391042Z", "version": "2.0.3"}}]}, "published": "2026-05-20T10:16:27.477", "references": [{"source": "sep@nlnetlabs.nl", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42534.txt"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:24013"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:36320"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:36777"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/errata/RHSA-2026:37282"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://access.redhat.com/security/cve/CVE-2026-42534"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2480131"}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42534.json"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-440"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-911"}], "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,1.25.1)"}}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 97.0, "source": "matching"}]}, "original": {"product": "Unbound", "source": "cna", "vendor": "NLnet Labs"}, "product": "unbound", "vendor": "nlnetlabs"}], "created": "2026-05-20T11:30:26.139533+00:00", "updated": "2026-08-14T03:00:04.592213+00:00", "vendors": ["nlnetlabs", "nlnetlabs$PRODUCT$unbound"]}