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

Vulnerability from cvelistv5 – Published: 2026-07-09 21:01 – Updated: 2026-07-10 14:21
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
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
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
To clipboard 

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\"providerUrgency\": \"GREEN\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"HIGH\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"MODERATE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"Juniper Networks\", \"product\": \"Junos OS\", \"versions\": [{\"status\": \"affected\", \"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\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"22.3R1\", \"versionType\": \"custom\"}], \"defaultStatus\": \"unaffected\"}, {\"vendor\": \"Juniper Networks\", \"product\": \"Junos OS Evolved\", \"versions\": [{\"status\": \"affected\", \"version\": \"23.2\", \"lessThan\": \"23.2R2-S7-EVO\", \"versionType\": \"custom\"}, {\"status\": \"affected\", \"version\": \"23.4\", \"lessThan\": \"23.4R2-S8-EVO\", \"versionType\": \"custom\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"22.3R1-EVO\", \"versionType\": \"custom\"}], \"defaultStatus\": \"unaffected\"}], \"exploits\": [{\"lang\": \"en\", \"value\": \"Juniper SIRT is not aware of any malicious exploitation of this vulnerability.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Juniper SIRT is not aware of any malicious exploitation of this vulnerability.\", \"base64\": false}]}], \"solutions\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"The following software releases have been updated to resolve this specific issue:\u003cbr\u003eJunos OS: 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8, 24.2R1, and all subsequent releases.\\n\u003cbr\u003e\\nJunos OS Evolved: 23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R1-EVO, and all subsequent releases.\", \"base64\": false}]}], \"datePublic\": \"2026-07-08T16:00:00.000Z\", \"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\"]}], \"workarounds\": [{\"lang\": \"en\", \"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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003eThere are no direct workarounds for this issue.\u003cbr\u003e\u003cbr\u003e\\n\\n\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003eOne of the following mitigations will prevent malicious exploitation:\u003c/span\u003e\u003cbr\u003e\u003cul\u003e\u003c/ul\u003e\u003cul\u003e\u003c/ul\u003e\u003cul\u003e\u003cli\u003eUse access lists or firewall filters to limit access to the CLI only from trusted hosts and administrators.\u003c/li\u003e\u003cli\u003eUtilize command authorization to limit the ability to enter config mode to trusted administrators.\u003c/li\u003e\u003c/ul\u003e\u003c/span\u003e\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"Vulnogram 0.1.0-dev\"}, \"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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"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\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-476\", \"description\": \"CWE-476 NULL Pointer Dereference\"}]}], \"providerMetadata\": {\"orgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"shortName\": \"juniper\", \"dateUpdated\": \"2026-07-09T21:01:31.334Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-21901\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-10T14:21:31.624Z\", \"dateReserved\": \"2026-01-05T17:32:48.709Z\", \"assignerOrgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"datePublished\": \"2026-07-09T21:01:31.334Z\", \"assignerShortName\": \"juniper\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.