CVE-2021-34737

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This vulnerability exists because certain DHCPv4 messages are improperly validated when they are processed by an affected device. An attacker could exploit this vulnerability by sending a malformed DHCPv4 message to an affected device. A successful exploit could allow the attacker to cause a NULL pointer dereference, resulting in a crash of the dhcpd process. While the dhcpd process is restarting, which may take up to approximately two minutes, DHCPv4 server services are unavailable on the affected device. This could temporarily prevent network access to clients that join the network during that time period. Note: Only the dhcpd process crashes and eventually restarts automatically. The router does not reload."}, {"lang": "es", "value": "Una vulnerabilidad en la funci\u00f3n de servidor DHCP versi\u00f3n 4 (DHCPv4) de Cisco IOS XR Software podr\u00eda permitir a un atacante remoto no autenticado desencadenar un bloqueo del proceso dhcpd, resultando en una condici\u00f3n de denegaci\u00f3n de servicio (DoS). Esta vulnerabilidad se presenta porque determinados mensajes DHCPv4 se comprueban inapropiadamente cuando son procesados por un dispositivo afectado. Un atacante podr\u00eda explotar esta vulnerabilidad enviando un mensaje DHCPv4 malformado a un dispositivo afectado. Una explotaci\u00f3n con \u00e9xito podr\u00eda permitir al atacante causar una desreferencia del puntero NULL, resultando en un bloqueo del proceso dhcpd. Mientras el proceso dhcpd se reinicia, lo que puede tardar hasta aproximadamente dos minutos, los servicios del servidor DHCPv4 no est\u00e1n disponibles en el dispositivo afectado. Esto podr\u00eda impedir temporalmente el acceso a la red a los clientes que se unan a ella durante ese periodo de tiempo. Nota: S\u00f3lo el proceso dhcpd se bloquea y finalmente se reinicia autom\u00e1ticamente. El router no se recarga"}], "id": "CVE-2021-34737", "lastModified": "2026-06-17T03:56:27.617", "metrics": {"cvssMetricV2": [{"acInsufInfo": false, "baseSeverity": "MEDIUM", "cvssData": {"accessComplexity": "LOW", "accessVector": "NETWORK", "authentication": "NONE", "availabilityImpact": "PARTIAL", "baseScore": 5.0, "confidentialityImpact": "NONE", "integrityImpact": "NONE", "vectorString": "AV:N/AC:L/Au:N/C:N/I:N/A:P", "version": "2.0"}, "exploitabilityScore": 10.0, "impactScore": 2.9, "obtainAllPrivilege": false, "obtainOtherPrivilege": false, "obtainUserPrivilege": false, "source": "nvd@nist.gov", "type": "Primary", "userInteractionRequired": false}], "cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 5.8, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "psirt@cisco.com", "type": "Secondary"}, {"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": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-34737", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-11-07T21:54:21.168817Z", "version": "2.0.3"}}]}, "published": "2021-09-09T05:15:11.963", "references": [{"source": "psirt@cisco.com", "tags": ["Vendor Advisory"], "url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dhcp-dos-pjPVReLU"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Vendor Advisory"], "url": "https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dhcp-dos-pjPVReLU"}], "sourceIdentifier": "psirt@cisco.com", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-476"}], "source": "psirt@cisco.com", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-476"}], "source": "nvd@nist.gov", "type": "Primary"}]}

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