CVE-2026-21901

published 2026-07-09

CVE-2026-21901: A NULL Pointer Dereference vulnerability in the management daemon (mgd) of Juniper Networks Junos OS and Junos OS Evolved allows a local, high-privileged…

Priority P4 19 medium 4.4 CVSS 3.1

AV L AC L PR H UI N S U C N I N A H

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.

Affected

6 ranges

Vendor	Product	Version range	Fixed in
juniper_networks	junos_os	>= 22.3 < 22.3R3-S5	22.3R3-S5
juniper_networks	junos_os	>= 22.4 < 22.4R3-S10	22.4R3-S10
juniper_networks	junos_os	>= 23.2 < 23.2R2-S7	23.2R2-S7
juniper_networks	junos_os	>= 23.4 < 23.4R2-S8	23.4R2-S8
juniper_networks	junos_os_evolved	>= 23.2 < 23.2R2-S7-EVO	23.2R2-S7-EVO
juniper_networks	junos_os_evolved	>= 23.4 < 23.4R2-S8-EVO	23.4R2-S8-EVO

CVSS provenance

nvd v3.1 4.4 MEDIUM CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

nvd v4.0 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/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

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