CVE-2026-50046

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Unbound", "vendor": "NLnet Labs", "versions": [{"lessThan": "1.25.2", "status": "affected", "version": "1.15.0", "versionType": "semver"}]}], "source": "sep@nlnetlabs.nl"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*", "matchCriteriaId": "16043273-E324-4533-93D1-27C32803A2F9", "versionEndExcluding": "1.25.2", "versionStartIncluding": "1.15.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound 1.15.0 up to and including 1.25.1, the TLS server name used for DNS-over-TLS (DoT) forwarded queries is tied to a struct's ('serviced_query') lifetime but also referenced by another struct ('waiting_tcp'). When the owning struct is jostled out of the mesh while the DoT TCP stream is still handshaking it frees the storage behind the referenced string and if the TLS stream then errors out, it dereferences the freed pointer. The dereference is read-only and the practical impact is a daemon crash resulting in denial of service. A malicious actor that knows a DoT forwarding/stub Unbound's configuration could exploit the vulnerability by quering records in the appropriate zone while keeping Unbound uder pressure so that the jostle logic kicks in. If answers for the vulnerable zone are slow, the likelihood of jostling such queries is higher, although the timing of the jostle needs to be precise. Requirements for a vulnerable Unbound is the existence of a stub/forward zone configured for DoT together with a configured '#authname' suffix on the server identification. The connectivity to the server needs to exhibit a transient failure at the correct time in order to kick off the vulnerable error path."}, {"lang": "es", "value": "En NLnet Labs Unbound 1.15.0 hasta la versi\u00f3n 1.25.1 inclusive, el nombre del servidor TLS utilizado para consultas reenviadas de DNS-over-TLS (DoT) est\u00e1 vinculado al ciclo de vida de una estructura (\u2019serviced_query\u2019) pero tambi\u00e9n referenciado por otra estructura (\u2019waiting_tcp\u2019). Cuando la estructura propietaria es desalojada de la malla mientras el flujo TCP de DoT a\u00fan est\u00e1 realizando el \u2019handshake\u2019, libera el almacenamiento detr\u00e1s de la cadena referenciada y, si el flujo TLS luego falla, desreferencia el puntero liberado. La desreferencia es de solo lectura y el impacto pr\u00e1ctico es un fallo del demonio que resulta en denegaci\u00f3n de servicio. Un actor malicioso que conoce la configuraci\u00f3n de un Unbound de reenv\u00edo/stub de DoT podr\u00eda explotar la vulnerabilidad consultando registros en la zona apropiada mientras mantiene a Unbound bajo presi\u00f3n para que la l\u00f3gica de desalojo se active. Si las respuestas para la zona vulnerable son lentas, la probabilidad de desalojar dichas consultas es mayor, aunque el momento del desalojo debe ser preciso. Los requisitos para un Unbound vulnerable son la existencia de una zona stub/forward configurada para DoT junto con un sufijo \u2019#authname\u2019 configurado en la identificaci\u00f3n del servidor. La conectividad al servidor necesita exhibir un fallo transitorio en el momento correcto para activar la ruta de error vulnerable."}], "id": "CVE-2026-50046", "lastModified": "2026-10-24T13:10:00.147", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 5.9, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 3.6, "source": "sep@nlnetlabs.nl", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-50046", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-07-22T18:57:24.481710Z", "version": "2.0.3"}}]}, "published": "2026-07-22T14:17:20.117", "references": [{"source": "sep@nlnetlabs.nl", "tags": ["Vendor Advisory"], "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50046.txt"}], "sourceIdentifier": "sep@nlnetlabs.nl", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "sep@nlnetlabs.nl", "type": "Secondary"}]}

{"bugzilla": {"description": "unbound: Unbound: Denial of Service due to freed pointer dereference in DNS-over-TLS handling", "id": "2506138", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2506138"}, "csaw": false, "cvss3": {"cvss3_base_score": "3.7", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-416", "details": ["A use-after-free flaw was found in Unbound's DNS-over-TLS (DoT) forwarded query handling. A remote attacker can exploit a timing error during TLS handshake failures on a server under load to trigger a daemon crash, resulting in a Denial of Service (DoS)."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, avoid configuring Unbound with a `#authname` suffix in DNS-over-TLS (DoT) forwarding or stub zones if not strictly required. If the `#authname` suffix is necessary, restrict network access to the Unbound instance to trusted clients only. This may involve configuring firewall rules to limit inbound connections to the DoT port (typically 853) from known, secure sources. After modifying Unbound's configuration, the service must be reloaded or restarted for the changes to take effect. This action may temporarily interrupt DNS resolution services."}, "name": "CVE-2026-50046", "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": "Not affected", "package_name": "unbound", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "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": "2026-07-22T13:08:08Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-50046\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-50046\nhttps://www.nlnetlabs.nl/downloads/unbound/CVE-2026-50046.txt"], "statement": "Unbound installations within Red Hat environments are vulnerable to a denial of service, leading to a daemon crash, only when specifically configured with DNS-over-TLS (DoT) forwarding or stub zones that include an `#authname` suffix. Exploitation by a remote attacker necessitates precise timing during transient network failures. Default Unbound configurations, which do not employ DoT forwarding or stub zones with `#authname`, are not affected. Hence, this is rated having low impact.", "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.15.0,1.25.2)"}}], "enrichment": {"confidence": 97.0, "confidence_source": "matching", "scores": [{"score": 97.0, "source": "matching"}]}, "original": {"product": "Unbound", "source": "cna", "vendor": "NLnet Labs"}, "product": "unbound", "vendor": "nlnetlabs"}], "created": "2026-07-23T19:00:17.242987+00:00", "updated": "2026-08-04T00:00:09.733214+00:00", "vendors": ["nlnetlabs", "nlnetlabs$PRODUCT$unbound"]}