CVE-2026-21910

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"text/html", "value": "<span style=\"background-color: rgb(255, 255, 255);\"><span style=\"background-color: rgb(255, 255, 255);\">An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms allows an unauthenticated network-adjacent attacker&nbsp;flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).</span><br></span><br>On all EX4k and QFX5k platforms, a link flap in an\n\nEVPN-VXLAN configuration Link Aggregation Group (LAG)\nresults in Inter-VNI traffic dropping when there are multiple load-balanced next-hop routes for the same destination.<br><br>This issue is only applicable to&nbsp;systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.<br><br>Service can only be restored by restarting the affected FPC via the '<tt>request chassis fpc restart slot &lt;slot-number&gt;</tt>' command.<br><br><p>This issue affects Junos OS \n\non EX4k and QFX5k Series:&nbsp;</p><p></p><ul><li>all versions before 21.4R3-S12,&nbsp;</li><li>all versions of 22.2</li><li>from 22.4 before 22.4R3-S8,&nbsp;</li><li>from 23.2 before 23.2R2-S5,&nbsp;</li><li>from 23.4 before 23.4R2-S5,&nbsp;</li><li>from 24.2 before 24.2R2-S3,</li><li>from 24.4 before 24.4R2.</li></ul><p></p>"}], "value": "An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms allows an unauthenticated network-adjacent attacker\u00a0flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).\n\nOn all EX4k and QFX5k platforms, a link flap in an\n\nEVPN-VXLAN configuration Link Aggregation Group (LAG)\nresults in Inter-VNI traffic dropping when 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"descriptions": [{"lang": "en", "value": "An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms allows an unauthenticated network-adjacent attacker\u00a0flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).\n\nOn all EX4k and QFX5k platforms, a link flap in an\n\nEVPN-VXLAN configuration Link Aggregation Group (LAG)\nresults in Inter-VNI traffic dropping when there are multiple load-balanced next-hop routes for the same destination.\n\nThis issue is only applicable to\u00a0systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.\n\nService can only be restored by restarting the affected FPC via the 'request chassis fpc restart slot <slot-number>' command.\n\nThis issue affects Junos OS \n\non EX4k and QFX5k Series:\u00a0\n\n\n\n * all versions before 21.4R3-S12,\u00a0\n * all versions of 22.2\n * from 22.4 before 22.4R3-S8,\u00a0\n * from 23.2 before 23.2R2-S5,\u00a0\n * from 23.4 before 23.4R2-S5,\u00a0\n * from 24.2 before 24.2R2-S3,\n * from 24.4 before 24.4R2.", "supportingMedia": [{"type": "text/html", "value": "<span style=\"background-color: rgb(255, 255, 255);\"><span style=\"background-color: rgb(255, 255, 255);\">An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms allows an unauthenticated network-adjacent attacker&nbsp;flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).</span><br></span><br>On all EX4k and QFX5k platforms, a link flap in an\n\nEVPN-VXLAN configuration Link Aggregation Group (LAG)\nresults in Inter-VNI traffic dropping when there are multiple load-balanced next-hop routes for the same destination.<br><br>This issue is only applicable to&nbsp;systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.<br><br>Service can only be restored by restarting the affected FPC via the '<tt>request chassis fpc restart slot &lt;slot-number&gt;</tt>' command.<br><br><p>This issue affects Junos OS \n\non EX4k and QFX5k Series:&nbsp;</p><p></p><ul><li>all versions before 21.4R3-S12,&nbsp;</li><li>all versions of 22.2</li><li>from 22.4 before 22.4R3-S8,&nbsp;</li><li>from 23.2 before 23.2R2-S5,&nbsp;</li><li>from 23.4 before 23.4R2-S5,&nbsp;</li><li>from 24.2 before 24.2R2-S3,</li><li>from 24.4 before 24.4R2.</li></ul><p></p>", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-754", "description": "CWE-754 Improper Check for Unusual or Exceptional Conditions"}]}], "configurations": [{"lang": "en", 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Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms allows an unauthenticated network-adjacent attacker\u00a0flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).\n\nOn all EX4k and QFX5k platforms, a link flap in an\n\nEVPN-VXLAN configuration Link Aggregation Group (LAG)\nresults in Inter-VNI traffic dropping when there are multiple load-balanced next-hop routes for the same destination.\n\nThis issue is only applicable to\u00a0systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.\n\nService can only be restored by restarting the affected FPC via the 'request chassis fpc restart slot <slot-number>' command.\n\nThis issue affects Junos OS \n\non EX4k and QFX5k Series:\u00a0\n\n\n\n * all versions before 21.4R3-S12,\u00a0\n * all versions of 22.2\n * from 22.4 before 22.4R3-S8,\u00a0\n * from 23.2 before 23.2R2-S5,\u00a0\n * from 23.4 before 23.4R2-S5,\u00a0\n * from 24.2 before 24.2R2-S3,\n * from 24.4 before 24.4R2."}, {"lang": "es", "value": "Una vulnerabilidad de comprobaci\u00f3n incorrecta de condiciones inusuales o excepcionales en el motor de reenv\u00edo de paquetes (PFE) de Juniper Networks Junos OS en plataformas de las series EX4k y QFX5k permite a un atacante no autenticado adyacente a la red que hace fluctuar una interfaz causar la ca\u00edda del tr\u00e1fico entre identificadores de red VXLAN (VNI), lo que lleva a una denegaci\u00f3n de servicio (DoS).\n\nEn todas las plataformas EX4k y QFX5k, una fluctuaci\u00f3n de enlace en un Grupo de Agregaci\u00f3n de Enlaces (LAG) con configuraci\u00f3n EVPN-VXLAN resulta en la ca\u00edda del tr\u00e1fico Inter-VNI cuando hay m\u00faltiples rutas de siguiente salto con balanceo de carga para el mismo destino.\n\nEste problema solo es aplicable a sistemas que soportan Grupos de Agregaci\u00f3n de Enlaces de Puerto Virtual EVPN-VXLAN (VPLAG), como los QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400 y EX4650.\n\nEl servicio solo puede restaurarse reiniciando la FPC afectada mediante el comando 'request chassis fpc restart slot '.\n\nEste problema afecta a Junos OS en las series EX4k y QFX5k:\n\n * todas las versiones anteriores a 21.4R3-S12,\n * todas las versiones de 22.2\n * desde 22.4 anteriores a 22.4R3-S8,\n * desde 23.2 anteriores a 23.2R2-S5,\n * desde 23.4 anteriores a 23.4R2-S5,\n * desde 24.2 anteriores a 24.2R2-S3,\n * desde 24.4 anteriores a 24.4R2."}], "id": "CVE-2026-21910", "lastModified": "2026-06-17T10:19:08.410", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "ADJACENT_NETWORK", "availabilityImpact": "HIGH", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/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": "USER", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "ADJACENT", "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": "NONE", "providerUrgency": "GREEN", "subAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/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:U/V:X/RE:M/U:Green", "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-2026-21910", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-01-15T20:51:52.841479Z", "version": "2.0.3"}}]}, "published": "2026-01-15T21:16:06.920", "references": [{"source": "sirt@juniper.net", "tags": ["Vendor Advisory"], "url": "https://kb.juniper.net/JSA106009"}, {"source": "sirt@juniper.net", "tags": ["Vendor Advisory"], "url": "https://supportportal.juniper.net/JSA106009"}], "sourceIdentifier": "sirt@juniper.net", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-754"}], "source": "sirt@juniper.net", "type": "Secondary"}]}

{}

{"analysis": {"en": {"generated_at": "2026-04-18T19:57:10.989118+00:00", "value": {"mitigation_remediation": ["Apply a Juniper update to Junos OS 21.4R3\u2011S12 or any later release that includes the fix for this issue", "If a patch cannot be applied immediately, temporarily restore services by restarting the affected Fabric Processing Card with the command 'request chassis fpc restart slot <slot-number>'", "Avoid or limit interface flapping on EVPN\u2011VXLAN interfaces until the patch is applied"], "summary": {"action": "Immediate Patch", "impact": "Denial of Service via inter\u2011VNI traffic drop"}, "threat_synthesis": {"affected_systems": "The flaw targets Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms, specifically the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650 devices. All software versions before 21.4R3\u2011S12, the entirety of 22.2, versions of 22.4 up to 22.4R3\u2011S8, versions of 23.2 up to 23.2R2\u2011S5, versions of 23.4 up to 23.4R2\u2011S5, versions of 24.2 up to 24.2R2\u2011S3, and versions of 24.4 up to 24.4R2 are impacted.", "description_and_impact": "An Improper Check for Unusual or Exceptional Conditions flaw in the packet forwarding engine of Juniper Networks Junos OS allows an unauthenticated network\u2011adjacent attacker to cause traffic between VXLAN Network Identifiers to drop with a simple interface flap. The resulting denial of service interrupts inter\u2011VNI communication, impacting network availability on affected chassis. This vulnerability is captured by CWE\u2011754, which denotes failure to validate exceptional conditions during forwarding logic.", "risk_and_exploitability": "The CVSS score of 7.1 indicates medium\u2011to\u2011high severity, but the EPSS score of less than 1% suggests a presently low exploitation probability. The vulnerability is not listed in the CISA KEV catalog. An unauthenticated network\u2011adjacent attacker can trigger the issue by flapping an interface without privileged credentials, leading to a denial of service. The vulnerability can be neutralised by restarting the affected Fabric Processing Card, but permanent mitigation requires upgrading to a release that contains the fix."}}}}, "created": "2026-01-16T13:42:54.031326+00:00", "updated": "2026-04-18T20:00:09.310758+00:00", "vendors": ["juniper", "juniper$PRODUCT$ex-series", "juniper$PRODUCT$ex4100", "juniper$PRODUCT$ex4300", "juniper$PRODUCT$ex4400", "juniper$PRODUCT$ex4650", "juniper$PRODUCT$junos_os", "juniper$PRODUCT$qfx5110", "juniper$PRODUCT$qfx5120", "juniper$PRODUCT$qfx5200", "juniper_networks", "juniper_networks$PRODUCT$junos_os"]}