CVE-2026-55717

{"id": "CVE-2026-55717", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-55717", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-07-22T14:07:12.831423Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "sep@nlnetlabs.nl", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.9, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 2.2}]}, "affected": [{"source": "sep@nlnetlabs.nl", "affectedData": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"status": "affected", "version": "1.10.0", "lessThan": "1.25.2", "versionType": "semver"}], "defaultStatus": "unaffected"}]}], "published": "2026-07-22T14:17:21.537", "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55717.txt", "tags": ["Vendor Advisory"], "source": "sep@nlnetlabs.nl"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "sep@nlnetlabs.nl", "description": [{"lang": "en", "value": "CWE-476"}]}], "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: <net> redirect' /'response-ip-data: <net> CNAME <target>' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash."}, {"lang": "es", "value": "En NLnet Labs Unbound 1.10.0 hasta la versi\u00f3n 1.25.1 inclusive, cuando se configura \u2019serve-expired: yes\u2019 junto con una regla \u2019response-ip: [net] redirect\u2019 / \u2019response-ip-data: [net] CNAME [target]\u2019 (o su equivalente RPZ \u2019rpz-cname-override\u2019), un cliente remoto que controla cualquier dominio delegado puede provocar la ca\u00edda del demonio. La funci\u00f3n de callback serve-expired-client-timeout ejecuta un bucle de dos pasadas para seguir el alias CNAME generado por respip; en la segunda pasada, reinicia \u2019alias_rrset\u2019 pero no \u2019partial_rep\u2019. Posteriormente, esta inconsistencia conduce a una desreferencia de puntero NULL y a una ca\u00edda eventual. Un actor malicioso puede explotar la vulnerabilidad controlando cualquier zona que responda con un registro A/AAAA que se encuentre dentro de la subred response-ip/rpz configurada. Al retrasar la respuesta cuando el registro anterior ha expirado, se toma la ruta vulnerable de \u2019serve-expired-client-timeout\u2019, lo que lleva a una denegaci\u00f3n de servicio a trav\u00e9s de la ca\u00edda del servidor."}], "lastModified": "2026-10-24T13:10:00.147", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "4B6C880D-74C8-4AA4-AA06-CF117E87BA82", "versionEndExcluding": "1.25.2", "versionStartIncluding": "1.10.0"}], "operator": "OR"}]}], "sourceIdentifier": "sep@nlnetlabs.nl"}