CVE-2026-21901: CWE-476 NULL Pointer Dereference in Juniper Networks Junos OS
CVE-2026-21901 is a NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved. A local, high-privileged user can trigger this by setting or deactivating a specific SSH configuration parameter, causing the mgd process to crash and restart. Repeated execution of these commands results in a sustained Denial of Service (DoS). This affects multiple versions of Junos OS and Junos OS Evolved starting from 22.3 and 22.3R1-EVO respectively, up to but not including certain patched releases. The vulnerability has a CVSS score of 4.4, indicating medium severity.
AI Analysis
Technical Summary
This vulnerability involves a NULL pointer dereference in the mgd process of Juniper Networks Junos OS and Junos OS Evolved. When a local, high-privileged attacker modifies a specific 'system services ssh' configuration parameter, the mgd process attempts to dereference a null pointer in an SSH-related function, causing the process to crash and restart. Continuous triggering leads to a sustained Denial of Service condition. Affected versions include Junos OS from 22.3 before 22.3R3-S5, 22.4 before 22.4R3-S10, 23.2 before 23.2R2-S7, and 23.4 before 23.4R2-S8; and Junos OS Evolved from 22.3R1-EVO before 23.2R2-S7-EVO and 23.4 before 23.4R2-S8-EVO. Versions prior to 22.3R1 and 22.3R1-EVO are not affected.
Potential Impact
The vulnerability allows a local, high-privileged user to cause the mgd process to crash and restart by exploiting a NULL pointer dereference. This results in a Denial of Service (DoS) condition, disrupting management operations on affected Junos OS and Junos OS Evolved devices. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is provided in the available data. Until a patch is available, restrict local high-privileged access to trusted users only to prevent exploitation.
CVE-2026-21901: CWE-476 NULL Pointer Dereference in Juniper Networks Junos OS
Description
CVE-2026-21901 is a NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved. A local, high-privileged user can trigger this by setting or deactivating a specific SSH configuration parameter, causing the mgd process to crash and restart. Repeated execution of these commands results in a sustained Denial of Service (DoS). This affects multiple versions of Junos OS and Junos OS Evolved starting from 22.3 and 22.3R1-EVO respectively, up to but not including certain patched releases. The vulnerability has a CVSS score of 4.4, indicating medium severity.
CVSS v3.1
Score 4.4medium
Affected software
pkg:github/orangecertcc/security-researchRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves a NULL pointer dereference in the mgd process of Juniper Networks Junos OS and Junos OS Evolved. When a local, high-privileged attacker modifies a specific 'system services ssh' configuration parameter, the mgd process attempts to dereference a null pointer in an SSH-related function, causing the process to crash and restart. Continuous triggering leads to a sustained Denial of Service condition. Affected versions include Junos OS from 22.3 before 22.3R3-S5, 22.4 before 22.4R3-S10, 23.2 before 23.2R2-S7, and 23.4 before 23.4R2-S8; and Junos OS Evolved from 22.3R1-EVO before 23.2R2-S7-EVO and 23.4 before 23.4R2-S8-EVO. Versions prior to 22.3R1 and 22.3R1-EVO are not affected.
Potential Impact
The vulnerability allows a local, high-privileged user to cause the mgd process to crash and restart by exploiting a NULL pointer dereference. This results in a Denial of Service (DoS) condition, disrupting management operations on affected Junos OS and Junos OS Evolved devices. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is provided in the available data. Until a patch is available, restrict local high-privileged access to trusted users only to prevent exploitation.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- juniper
- Date Reserved
- 2026-01-05T17:32:48.709Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a50101d68715ace43153c4d
Added to database: 07/09/2026, 21:18:21 UTC
Last enriched: 07/09/2026, 21:33:33 UTC
Last updated: 07/09/2026, 22:35:06 UTC
Views: 3
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