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Vulnerability record · CVE-2026-21901 · published 9 July 2026

CVE-2026-21901: Juniper junos null pointer dereference vulnerability

Juniper · Junos

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.

6.7 CVSS 4.0 Medium EPSS 0.17% · top 94.9% CWE-476 · NULL pointer dereference
6.7CVSS 4.0 base score
0.17%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
3References, 2 tagged exploit
26 Aug 2026Last modified by NVD

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). 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.

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:

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6 MitigationExploitThird Party Advisory
https://supportportal.juniper.net/JSA110072 Vendor Advisory
https://github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-w2rc-hpj6 MitigationExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-21901), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.