{"id":"CVE-2026-21901","state":"PUBLISHED","title":"Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash","description":"A NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, high-privileged attacker setting or deactivating a specific SSH configuration parameter to create a Denial of Service (DoS).\n\nA local high-privileged user configuring or deactivating a specific 'system services ssh' configuration parameter can exploit a null pointer dereference in one of the functions used by SSH. The function attempts to dereference a null pointer when accessing certain configuration data, resulting in an mgd process crash and restart. Continued execution of these configuration commands will create a sustained Denial of Service (DoS) condition.\n\nThis issue affects:\nJunos OS:\n\n\n  *  from 22.3 before 22.3R3-S5;\n  *  from 22.4 before 22.4R3-S10;\n  *  from 23.2 before 23.2R2-S7;\n  *  from 23.4 before 23.4R2-S8.\n\n\n\n\nThis issue does not affect Junos OS before 22.3R1.\n\n\n\nJunos OS Evolved:\n  *  from 22.3R1-EVO before 23.2R2-S7-EVO;\n  *  from 23.4 before 23.4R2-S8-EVO.\n\n\nThis issue does not affect Junos OS Evolved before 22.3R1-EVO.","publishedAt":"2026-07-09T21:01:31.334Z","updatedAt":"2026-07-10T14:21:31.624Z","severity":{"score":6.7,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/AU:Y/R:A/V:D/RE:M/U:Green","source":"juniper"},"assigner":"juniper","products":["Juniper Networks Junos OS","Juniper Networks Junos OS Evolved"],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"22.3","status":"affected","lessThan":"22.3R3-S5","versionType":"custom"},{"version":"22.4","status":"affected","lessThan":"22.4R3-S10","versionType":"custom"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S7","versionType":"custom"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S8","versionType":"custom"},{"version":"0","status":"unaffected","lessThan":"22.3R1","versionType":"custom"}]},{"vendor":"Juniper Networks","product":"Junos OS Evolved","defaultStatus":"unaffected","versions":[{"version":"23.2","status":"affected","lessThan":"23.2R2-S7-EVO","versionType":"custom"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S8-EVO","versionType":"custom"},{"version":"0","status":"unaffected","lessThan":"22.3R1-EVO","versionType":"custom"}]}],"references":["https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6","https://supportportal.juniper.net/JSA110072"],"weaknesses":["CWE-476"],"ingestedAt":"2026-10-29T20:11:10.572Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/21xxx/CVE-2026-21901.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-21901","state":"PUBLISHED","datePublished":"2026-07-09T21:01:31.334Z","dateUpdated":"2026-07-10T14:21:31.624Z","assignerShortName":"juniper","assignerOrgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateReserved":"2026-01-05T17:32:48.709Z"},"containers":{"cna":{"title":"Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash","descriptions":[{"lang":"en","value":"A NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, high-privileged attacker setting or deactivating a specific SSH configuration parameter to create a Denial of Service (DoS).\n\nA local high-privileged user configuring or deactivating a specific 'system services ssh' configuration parameter can exploit a null pointer dereference in one of the functions used by SSH. The function attempts to dereference a null pointer when accessing certain configuration data, resulting in an mgd process crash and restart. Continued execution of these configuration commands will create a sustained Denial of Service (DoS) condition.\n\nThis issue affects:\nJunos OS:\n\n\n  *  from 22.3 before 22.3R3-S5;\n  *  from 22.4 before 22.4R3-S10;\n  *  from 23.2 before 23.2R2-S7;\n  *  from 23.4 before 23.4R2-S8.\n\n\n\n\nThis issue does not affect Junos OS before 22.3R1.\n\n\n\nJunos OS Evolved:\n  *  from 22.3R1-EVO before 23.2R2-S7-EVO;\n  *  from 23.4 before 23.4R2-S8-EVO.\n\n\nThis issue does not affect Junos OS Evolved before 22.3R1-EVO."}],"affected":[{"vendor":"Juniper Networks","product":"Junos OS","defaultStatus":"unaffected","versions":[{"version":"22.3","status":"affected","lessThan":"22.3R3-S5","versionType":"custom"},{"version":"22.4","status":"affected","lessThan":"22.4R3-S10","versionType":"custom"},{"version":"23.2","status":"affected","lessThan":"23.2R2-S7","versionType":"custom"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S8","versionType":"custom"},{"version":"0","status":"unaffected","lessThan":"22.3R1","versionType":"custom"}]},{"vendor":"Juniper Networks","product":"Junos OS Evolved","defaultStatus":"unaffected","versions":[{"version":"23.2","status":"affected","lessThan":"23.2R2-S7-EVO","versionType":"custom"},{"version":"23.4","status":"affected","lessThan":"23.4R2-S8-EVO","versionType":"custom"},{"version":"0","status":"unaffected","lessThan":"22.3R1-EVO","versionType":"custom"}]}],"references":[{"url":"https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6","tags":["third-party-advisory"]},{"url":"https://supportportal.juniper.net/JSA110072","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":4.4,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"HIGH","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:L/PR:H/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":"LOCAL","baseScore":6.7,"baseSeverity":"MEDIUM","privilegesRequired":"HIGH","providerUrgency":"GREEN","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"DIFFUSE","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/AU:Y/R:A/V:D/RE:M/U:Green","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"MODERATE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-476","description":"CWE-476 NULL Pointer Dereference","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"juniper","orgId":"8cbe9d5a-a066-4c94-8978-4b15efeae968","dateUpdated":"2026-07-09T21:01:31.334Z"},"credits":[{"lang":"en","type":"finder","value":"Juniper SIRT would like to acknowledge and thank Orange CERT-CC from the Orange group for responsibly reporting this vulnerability."}],"datePublic":"2026-07-08T16:00:00.000Z","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:<br>Junos OS: 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8, 24.2R1, and all subsequent releases.\n<br>\nJunos OS Evolved: 23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R1-EVO, and all subsequent releases."}],"value":"The following software releases have been updated to resolve this specific issue:\nJunos OS: 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8, 24.2R1, and all subsequent releases.\n\n\nJunos OS Evolved: 23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R1-EVO, and all subsequent releases."}],"source":{"advisory":"JSA110072","defect":["1779319"],"discovery":"EXTERNAL"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<span style=\"background-color: rgb(255, 255, 255);\">There are no direct workarounds for this issue.<br><br>\n\n<span style=\"background-color: rgb(255, 255, 255);\">One of the following mitigations will prevent malicious exploitation:</span><br><ul></ul><ul></ul><ul><li>Use access lists or firewall filters to limit access to the CLI only from trusted hosts and administrators.</li><li>Utilize command authorization to limit the ability to enter config mode to trusted administrators.</li></ul></span>"}],"value":"There are no direct workarounds for this issue.\n\n\n\nOne of the following mitigations will prevent malicious exploitation:\n\n\n\n\n  *  Use access lists or firewall filters to limit access to the CLI only from trusted hosts and administrators.\n  *  Utilize command authorization to limit the ability to enter config mode to trusted administrators."}],"x_generator":{"engine":"Vulnogram 0.1.0-dev"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-10T14:21:27.704515Z","id":"CVE-2026-21901","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-10T14:21:31.624Z"}}]}}}