CVE-2026-21921

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"matchCriteriaId": "9D7F0D73-85EE-4A07-B51B-6BF52ECBA75E", "vulnerable": true}, {"criteria": "cpe:2.3:o:juniper:junos_os_evolved:23.4:r1:*:*:*:*:*:*", "matchCriteriaId": "FE777A1F-9CD9-426E-AF1C-FBE01EB9A4A8", "vulnerable": true}, {"criteria": "cpe:2.3:o:juniper:junos_os_evolved:23.4:r1-s1:*:*:*:*:*:*", "matchCriteriaId": "7147BA60-30A5-4CED-9AAF-F6BEA0528B89", "vulnerable": true}, {"criteria": "cpe:2.3:o:juniper:junos_os_evolved:23.4:r1-s2:*:*:*:*:*:*", "matchCriteriaId": "6E5CE59B-14B2-4F4C-81B5-0430EC954956", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "A Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service (DoS).\n\nWhen telemetry collectors are frequently subscribing and unsubscribing to sensors continuously over a long period of time, telemetry-capable processes like chassisd, rpd or mib2d will crash and restart, which - depending on the process - can cause a complete outage until the system has recovered.\n\nThis issue affects:\n\n\u00a0Junos OS:\u00a0\n\n\n\n * all versions before 22.4R3-S8,\n * 23.2 versions before 23.2R2-S5,\n * 23.4 versions before 23.4R2;\n\n\n\n\nJunos OS Evolved:\n\n\n\n * all versions before 22.4R3-S8-EVO,\n * 23.2 versions before 23.2R2-S5-EVO,\n * 23.4 versions before 23.4R2-EVO."}, {"lang": "es", "value": "Una vulnerabilidad de Uso Despu\u00e9s de Liberar en el demonio de chasis (chassisd) de Juniper Networks Junos OS y Junos OS Evolved permite a un atacante basado en red autenticado con bajos privilegios causar una Denegaci\u00f3n de Servicio (DoS).\n\nCuando los recolectores de telemetr\u00eda se suscriben y anulan la suscripci\u00f3n a sensores frecuentemente y de forma continua durante un largo per\u00edodo de tiempo, los procesos con capacidad de telemetr\u00eda como chassisd, rpd o mib2d se bloquear\u00e1n y reiniciar\u00e1n, lo cual - dependiendo del proceso - puede causar una interrupci\u00f3n completa hasta que el sistema se haya recuperado.\n\nEste problema afecta:\n\nJunos OS:\n\n * todas las versiones anteriores a 22.4R3-S8,\n * versiones 23.2 anteriores a 23.2R2-S5,\n * versiones 23.4 anteriores a 23.4R2;\n\nJunos OS Evolved:\n\n * todas las versiones anteriores a 22.4R3-S8-EVO,\n * versiones 23.2 anteriores a 23.2R2-S5-EVO,\n * versiones 23.4 anteriores a 23.4R2-EVO."}], "id": "CVE-2026-21921", "lastModified": "2026-06-17T10:19:10.153", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "sirt@juniper.net", "type": "Secondary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "YES", "Recovery": "AUTOMATIC", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 7.1, "baseSeverity": "HIGH", "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": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/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:Y/R:A/V:X/RE:M/U:X", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "MODERATE"}, "source": "sirt@juniper.net", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-21921", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-01-15T20:54:58.001808Z", "version": "2.0.3"}}]}, "published": "2026-01-15T21:16:08.400", "references": [{"source": "sirt@juniper.net", "tags": ["Vendor Advisory"], "url": "https://kb.juniper.net/JSA106021"}, {"source": "sirt@juniper.net", "tags": ["Vendor Advisory"], "url": "https://supportportal.juniper.net/JSA106021"}], "sourceIdentifier": "sirt@juniper.net", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "sirt@juniper.net", "type": "Secondary"}]}

{}

{"analysis": {"en": {"generated_at": "2026-04-18T19:57:02.366110+00:00", "value": {"mitigation_remediation": ["Apply a Junos OS or Junos OS Evolved release that includes the fix (e.g., 22.4R3\u2011S8 / 22.4R3\u2011S8\u2011EVO, 23.2R2\u2011S5 / 23.2R2\u2011S5\u2011EVO, 23.4R2 / 23.4R2\u2011EVO, or newer releases).", "Disable non\u2011essential telemetry services such as chassisd, rpd, or mib2d if they are not required, thereby reducing the attack surface.", "Implement firewall or ACL rules to throttle telemetry subscription traffic, limiting the frequency of subscribe/unsubscribe requests until a patched build can be installed."], "summary": {"action": "Immediate Patch", "impact": "Denial\u2011of\u2011Service"}, "threat_synthesis": {"affected_systems": "The vulnerability affects Juniper Networks Junos OS and Junos OS Evolved. All builds prior to Junos OS 22.4R3\u2011S8, 23.2R2\u2011S5, and 23.4R2, as well as the corresponding Evolved releases 22.4R3\u2011S8\u2011EVO, 23.2R2\u2011S5\u2011EVO, and 23.4R2\u2011EVO, are susceptible. Vendor\u2011issued patched releases begin with 22.4R3\u2011S8\u00a0/\u00a022.4R3\u2011S8\u2011EVO, 23.2R2\u2011S5\u00a0/\u00a023.2R2\u2011S5\u2011EVO, 23.4R2\u00a0/\u00a023.4R2\u2011EVO and later.", "description_and_impact": "A use\u2011after\u2011free flaw (CWE-416) in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved permits an authenticated network\u2011based attacker with low privileges to trigger crashes in critical telemetry\u2011capable processes. When collectors repeatedly subscribe and unsubscribe to sensors over an extended period, components such as chassisd, rpd or mib2d crash and restart, potentially causing a full outage until the device recovers.", "risk_and_exploitability": "The CVSS score of 7.1 indicates a serious risk, and the EPSS score is reported to be below 1%, suggesting current exploitation is unlikely but possible. The vulnerability is not listed in CISA\u2019s KEV catalog, meaning known exploitation is not publicly confirmed. Attackers would need network reach, legitimate low\u2011privilege credentials, and the ability to repeatedly perform telemetry subscribe/unsubscribe operations to trigger the crash. No workaround is available, so the only effective defense is to apply the vendor\u2019s patch."}}}}, "created": "2026-01-16T13:42:59.396809+00:00", "updated": "2026-04-18T20:00:09.302618+00:00", "vendors": ["juniper_networks", "juniper_networks$PRODUCT$junos_os", "juniper_networks$PRODUCT$junos_os_evolved"]}