CVE-2026-21918

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"cpe:2.3:h:juniper:srx5400:-:*:*:*:*:*:*:*", "matchCriteriaId": "2FDDC897-747F-44DD-9599-7266F9B5B7B1", "vulnerable": false}, {"criteria": "cpe:2.3:h:juniper:srx5600:-:*:*:*:*:*:*:*", "matchCriteriaId": "68CA098D-CBE4-4E62-9EC0-43E1B6098710", "vulnerable": false}, {"criteria": "cpe:2.3:h:juniper:srx5800:-:*:*:*:*:*:*:*", "matchCriteriaId": "66F474D4-79B6-4525-983C-9A9011BD958B", "vulnerable": false}], "negate": false, "operator": "OR"}], "operator": "AND"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens. This causes flowd to crash and the respective FPC to restart.\n\n\n\n\n\nThis issue affects Junos OS on SRX and MX Series:\n\n\n\n * all versions before 22.4R3-S7,\n * 23.2 versions before 23.2R2-S3,\n * 23.4 versions before 23.4R2-S4,\n * 24.2 versions before 24.2R2."}, {"lang": "es", "value": "Una vulnerabilidad de doble liberaci\u00f3n en el demonio de procesamiento de flujo (flowd) de Juniper Networks Junos OS en las series SRX y MX permite a un atacante no autenticado y basado en red causar una Denegaci\u00f3n de Servicio (DoS). En todas las plataformas de las series SRX y MX, cuando durante el establecimiento de una sesi\u00f3n TCP se encuentra una secuencia espec\u00edfica de paquetes, ocurre una doble liberaci\u00f3n. Esto provoca que flowd se bloquee y que el FPC respectivo se reinicie.\n\nEste problema afecta a Junos OS en las series SRX y MX:\n\n * todas las versiones anteriores a 22.4R3-S7,\n * versiones 23.2 anteriores a 23.2R2-S3,\n * versiones 23.4 anteriores a 23.4R2-S4,\n * versiones 24.2 anteriores a 24.2R2."}], "id": "CVE-2026-21918", "lastModified": "2026-06-17T10:19:09.647", "metrics": {"cvssMetricV31": [{"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": "sirt@juniper.net", "type": "Secondary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "YES", "Recovery": "AUTOMATIC", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 8.7, "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": "NOT_DEFINED", "subAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/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: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-2026-21918", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-01-15T21:12:54.048156Z", "version": "2.0.3"}}]}, "published": "2026-01-15T21:16:08.050", "references": [{"source": "sirt@juniper.net", "tags": ["Vendor Advisory"], "url": "https://kb.juniper.net/JSA106018"}, {"source": "sirt@juniper.net", "tags": ["Vendor Advisory"], "url": "https://supportportal.juniper.net/JSA106018"}], "sourceIdentifier": "sirt@juniper.net", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-415"}], "source": "sirt@juniper.net", "type": "Secondary"}]}

{}

{"analysis": {"en": {"generated_at": "2026-04-18T05:56:02.826870+00:00", "value": {"mitigation_remediation": ["Upgrade every SRX and MX Series device to a fixed release\u2014any of 22.4R3\u2011S7, 23.2R2\u2011S3, 23.4R2\u2011S4, 24.2R2, 24.4R1 or later\u2014ensuring the binary includes the patch for flowd. ", "While the upgrade is pending, enforce strict access controls on interfaces that expose the device to untrusted networks. Use ACLs or firewall rules to block traffic that could generate the specific TCP session establishment pattern known to trigger the double\u2011free, focusing on limiting outbound TCP handshakes from non\u2011trusted sources. ", "Schedule a maintenance window to apply the firmware update, then verify stability by monitoring flowd logs and device performance for any recurrence of crashes."], "summary": {"action": "Patch Immediately", "impact": "Denial of Service through a double\u2011free in the flowd process"}, "threat_synthesis": {"affected_systems": "All Juniper Networks Junos OS on SRX and MX Series platforms are affected, including versions released before 22.4R3\u2011S7, before 23.2R2\u2011S3, before 23.4R2\u2011S4, and before 24.2R2. The update releases listed by Juniper\u201422.4R3\u2011S7, 23.2R2\u2011S3, 23.4R2\u2011S4, 24.2R2, 24.4R1, and any subsequent releases\u2014contain the fix.", "description_and_impact": "A double\u2011free flaw in the flow usage daemon of Juniper Networks Junos OS on SRX and MX series allows an unauthenticated, network\u2011based attacker to trigger a crash of flowd. When a specific sequence of TCP packets occurs during a TCP session establishment the flaw is triggered, causing flowd to terminate and the faulty forwarding plane card (FPC) to restart. This results in a denial\u2011of\u2011service condition for the affected device.", "risk_and_exploitability": "The vulnerability carries a CVSS score of 8.7, indicating high severity, while the EPSS score is below 1\u202f%, implying that true exploitation probability is low. The flaw is not currently in the CISA KEV catalog. Attackers can provoke the double\u2011free by sending a crafted TCP packet sequence across an unauthenticated network channel to the targeted device, so the threat is limited to networks with exposure to the SRX or MX device. Organizations should treat the risk as moderate to high and act promptly to apply the vendor\u2011supplied updates."}}}}, "created": "2026-01-16T13:43:00.110606+00:00", "updated": "2026-04-18T06:00:08.503676+00:00", "vendors": ["juniper_networks", "juniper_networks$PRODUCT$junos_os"]}