{"id":"CVE-2026-21901","aliases":["EUVD-2026-42697"],"status":"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.","severity":{"version":"4.0","score":6.7,"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00177,"percentile":0.07332,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-476"],"published":"2026-07-09T21:01:31Z","modified":"2026-08-26T17:48:51Z","products":[{"vendor":"juniper","product":"junos"},{"vendor":"juniper","product":"junos_os_evolved"},{"vendor":"juniper networks","product":"junos os"},{"vendor":"juniper networks","product":"junos os evolved"}],"references":[{"url":"https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6","tags":["third-party-advisory","exploit","Mitigation","Exploit","Third Party Advisory"]},{"url":"https://supportportal.juniper.net/JSA110072","tags":["vendor-advisory","Vendor Advisory"]}],"sources":{"cve":[{"id":"CVE-2026-21901","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.","status":"published","published":"2026-07-09T21:01:31.334Z","modified":"2026-07-10T14:21:31.624Z","cvss":[{"version":"4.0","score":6.7,"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","level":"medium","assessor":"cna"},{"version":"3.1","score":4.4,"vector":"CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-476"],"updated_at":"2026-11-02T13:41:42.05254Z"}],"euvd":[{"id":"EUVD-2026-42697","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.","status":"published","published":"2026-07-09T21:01:31Z","modified":"2026-07-10T14:21:31Z","cvss":[{"version":"4.0","score":6.7,"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","level":"medium"}],"updated_at":"2026-11-02T18:20:03.345658Z"}],"nvd":[{"id":"CVE-2026-21901","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.","status":"published","published":"2026-07-09T21:16:54.467Z","modified":"2026-08-26T17:48:51.667Z","cvss":[{"version":"4.0","score":6.7,"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/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:D/RE:M/U:Green","level":"medium","assessor":"secondary"},{"version":"3.1","score":4.4,"vector":"CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"}],"cwes":["CWE-476"],"updated_at":"2026-11-02T14:12:28.4135Z"}]}}