{"id":"CVE-2026-21918","state":"PUBLISHED","title":"Junos OS: SRX and MX Series: When TCP packets occur in a specific sequence flowd crashes","description":"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.","publishedAt":"2026-01-15T20:27:54.743Z","updatedAt":"2026-01-15T21:13:00.740Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"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/AU:Y/R:A/RE:M","source":"juniper"},"assigner":"juniper","products":["Juniper Networks Junos OS"],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"22.4R3-S7","versionType":"semver"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S3","versionType":"semver"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S4","versionType":"semver"},{"version":"24.2","status":"affected","lessThan":"24.2R2","versionType":"semver"}],"platforms":["SRX Series","MX Series"]}],"references":["https://supportportal.juniper.net/JSA106018","https://kb.juniper.net/JSA106018"],"weaknesses":["CWE-415"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/21xxx/CVE-2026-21918.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21918","state":"PUBLISHED","datePublished":"2026-01-15T20:27:54.743Z","dateUpdated":"2026-01-15T21:13:00.740Z","assignerShortName":"juniper","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateReserved":"2026-01-05T17:32:48.711Z"},"containers":{"cna":{"title":"Junos OS: SRX and MX Series: When TCP packets occur in a specific sequence flowd crashes","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."}],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"22.4R3-S7","versionType":"semver"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S3","versionType":"semver"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S4","versionType":"semver"},{"version":"24.2","status":"affected","lessThan":"24.2R2","versionType":"semver"}],"platforms":["SRX Series","MX Series"]}],"references":[{"url":"https://supportportal.juniper.net/JSA106018","tags":["vendor-advisory"]},{"url":"https://kb.juniper.net/JSA106018","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"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"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]},{"cvssV4_0":{"Automatable":"YES","Recovery":"AUTOMATIC","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":8.7,"baseSeverity":"HIGH","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/AU:Y/R:A/RE:M","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"MODERATE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-415","description":"CWE-415 Double Free","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"juniper","orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateUpdated":"2026-01-15T20:27:54.743Z"},"datePublic":"2026-01-14T17:00:00.000Z","exploits":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Juniper SIRT is not aware of any malicious exploitation of this vulnerability."}],"value":"Juniper SIRT is not aware of any malicious exploitation of this vulnerability."}],"solutions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"The following software releases have been updated to resolve this specific issue: 22.4R3-S7, 23.2R2-S3, 23.4R2-S4, 24.2R2, 24.4R1, and all subsequent releases."}],"value":"The following software releases have been updated to resolve this specific issue: 22.4R3-S7, 23.2R2-S3, 23.4R2-S4, 24.2R2, 24.4R1, and all subsequent releases."}],"source":{"advisory":"JSA106018","defect":["1834248"],"discovery":"USER"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"There are no known workarounds for this issue."}],"value":"There are no known workarounds for this issue."}],"x_generator":{"engine":"Vulnogram 0.1.0-dev"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-01-15T21:12:54.048156Z","id":"CVE-2026-21918","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-01-15T21:13:00.740Z"}}]}}}