CVE-2026-21901
Severity CVSS v4.0:
MEDIUM
Type:
CWE-476
NULL Pointer Dereference
Publication date:
09/07/2026
Last modified:
10/07/2026
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).<br />
<br />
A local high-privileged user configuring or deactivating a specific &#39;system services ssh&#39; 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.<br />
<br />
This issue affects:<br />
Junos OS:<br />
<br />
<br />
* from 22.3 before 22.3R3-S5;<br />
* from 22.4 before 22.4R3-S10;<br />
* from 23.2 before 23.2R2-S7;<br />
* from 23.4 before 23.4R2-S8.<br />
<br />
<br />
<br />
<br />
This issue does not affect Junos OS before 22.3R1.<br />
<br />
<br />
<br />
Junos OS Evolved:<br />
* from 22.3R1-EVO before 23.2R2-S7-EVO;<br />
* from 23.4 before 23.4R2-S8-EVO.<br />
<br />
<br />
This issue does not affect Junos OS Evolved before 22.3R1-EVO.
Impact
Base Score 4.0
6.70
Severity 4.0
MEDIUM
Base Score 3.x
4.40
Severity 3.x
MEDIUM