CVE-2026-21901 (GCVE-0-2026-21901)

Vulnerability from cvelistv5 – Published: 2026-07-09 21:01 – Updated: 2026-07-09 21:01
VLAI
Title
Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash
Summary
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). A 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. This issue affects: Junos OS: * from 22.3 before 22.3R3-S5; * from 22.4 before 22.4R3-S10; * from 23.2 before 23.2R2-S7; * from 23.4 before 23.4R2-S8. This issue does not affect Junos OS before 22.3R1. Junos OS Evolved: * from 22.3R1-EVO before 23.2R2-S7-EVO; * from 23.4 before 23.4R2-S8-EVO. This issue does not affect Junos OS Evolved before 22.3R1-EVO.
Severity
4.4 (Medium)
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
6.7 (Medium)
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
CWE
  • CWE-476 - NULL Pointer Dereference
Assigner
References
Impacted products
Vendor Product Version
Juniper Networks Junos OS Affected: 22.3 , < 22.3R3-S5 (custom)
Affected: 22.4 , < 22.4R3-S10 (custom)
Affected: 23.2 , < 23.2R2-S7 (custom)
Affected: 23.4 , < 23.4R2-S8 (custom)
Unaffected: 0 , < 22.3R1 (custom)
Create a notification for this product.
Juniper Networks Junos OS Evolved Affected: 23.2 , < 23.2R2-S7-EVO (custom)
Affected: 23.4 , < 23.4R2-S8-EVO (custom)
Unaffected: 0 , < 22.3R1-EVO (custom)
Create a notification for this product.
Date Public
2026-07-08 16:00
Credits
Juniper SIRT would like to acknowledge and thank Orange CERT-CC from the Orange group for responsibly reporting this vulnerability.
Show details on NVD website
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              "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\u0026nbsp;specific SSH configuration parameter to create a Denial of Service (DoS).\u003cbr\u003e\u003cbr\u003eA local high-privileged user configuring or deactivating a specific \u0027system services ssh\u0027 configuration parameter\u0026nbsp;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.\u0026nbsp;Continued execution of these configuration commands will create a sustained Denial of Service (DoS) condition.\u003cbr\u003e\u003cp\u003e\u003cbr\u003eThis issue affects:\u003cbr\u003eJunos OS:\u003cbr\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003efrom 22.3 before 22.3R3-S5;\u003c/li\u003e\u003cli\u003efrom 22.4 before 22.4R3-S10;\u003c/li\u003e\u003cli\u003efrom 23.2 before 23.2R2-S7;\u003c/li\u003e\u003cli\u003efrom 23.4 before 23.4R2-S8.\u003c/li\u003e\u003c/ul\u003e\n\nThis issue does not affect Junos OS before 22.3R1.\n\n\u003cbr\u003e\u003cbr\u003eJunos OS Evolved:\u003cbr\u003e\u003cul\u003e\u003cli\u003efrom 22.3R1-EVO before 23.2R2-S7-EVO;\u003c/li\u003e\u003cli\u003efrom 23.4 before 23.4R2-S8-EVO.\u003c/li\u003e\u003c/ul\u003eThis issue does not affect Junos OS Evolved before 22.3R1-EVO.\u003cp\u003e\u003c/p\u003e"
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          "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\u00a0specific SSH configuration parameter to create a Denial of Service (DoS).\n\nA local high-privileged user configuring or deactivating a specific \u0027system services ssh\u0027 configuration parameter\u00a0can 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.\u00a0Continued 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."
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    "dateReserved": "2026-01-05T17:32:48.709Z",
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    "state": "PUBLISHED"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-21901\",\"sourceIdentifier\":\"sirt@juniper.net\",\"published\":\"2026-07-09T21:16:54.467\",\"lastModified\":\"2026-07-09T21:16:54.467\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"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\u00a0specific SSH configuration parameter to create a Denial of Service (DoS).\\n\\nA local high-privileged user configuring or deactivating a specific \u0027system services ssh\u0027 configuration parameter\u00a0can 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.\u00a0Continued 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\":[{\"source\":\"sirt@juniper.net\",\"affectedData\":[{\"vendor\":\"Juniper Networks\",\"product\":\"Junos OS\",\"defaultStatus\":\"unaffected\",\"versions\":[{\"version\":\"22.3\",\"lessThan\":\"22.3R3-S5\",\"versionType\":\"custom\",\"status\":\"affected\"},{\"version\":\"22.4\",\"lessThan\":\"22.4R3-S10\",\"versionType\":\"custom\",\"status\":\"affected\"},{\"version\":\"23.2\",\"lessThan\":\"23.2R2-S7\",\"versionType\":\"custom\",\"status\":\"affected\"},{\"version\":\"23.4\",\"lessThan\":\"23.4R2-S8\",\"versionType\":\"custom\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"22.3R1\",\"versionType\":\"custom\",\"status\":\"unaffected\"}]},{\"vendor\":\"Juniper Networks\",\"product\":\"Junos OS Evolved\",\"defaultStatus\":\"unaffected\",\"versions\":[{\"version\":\"23.2\",\"lessThan\":\"23.2R2-S7-EVO\",\"versionType\":\"custom\",\"status\":\"affected\"},{\"version\":\"23.4\",\"lessThan\":\"23.4R2-S8-EVO\",\"versionType\":\"custom\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"22.3R1-EVO\",\"versionType\":\"custom\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"sirt@juniper.net\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"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/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\",\"baseScore\":6.7,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"NONE\",\"privilegesRequired\":\"HIGH\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"NONE\",\"vulnAvailabilityImpact\":\"HIGH\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"YES\",\"Recovery\":\"AUTOMATIC\",\"valueDensity\":\"DIFFUSE\",\"vulnerabilityResponseEffort\":\"MODERATE\",\"providerUrgency\":\"GREEN\"}}],\"cvssMetricV31\":[{\"source\":\"sirt@juniper.net\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":4.4,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"HIGH\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":0.8,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"sirt@juniper.net\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-476\"}]}],\"references\":[{\"url\":\"https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6\",\"source\":\"sirt@juniper.net\"},{\"url\":\"https://supportportal.juniper.net/JSA110072\",\"source\":\"sirt@juniper.net\"}]}}"
  }
}



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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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