Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash
Summary
| CVE | CVE-2026-21901 |
|---|---|
| State | PUBLISHED |
| Assigner | juniper |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-09 21:16:54 UTC |
| Updated | 2026-07-10 17:49:57 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 6.7 MEDIUM from [email protected]
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
EPSS: 0.001660000 probability, percentile 0.061060000 (date 2026-07-12)
Problem Types: CWE-476 | CWE-476 CWE-476 NULL Pointer Dereference
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 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/C... |
| 4.0 | CNA | CVSS | 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/... |
| 3.1 | [email protected] | Secondary | 4.4 | MEDIUM | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 4.4 | MEDIUM | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H |
CVSS v4.0 Breakdown
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
CVSS v3.1 Breakdown
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Juniper Networks | Junos OS | affected 22.3 22.3R3-S5 custom | Not specified |
| CNA | Juniper Networks | Junos OS | affected 22.4 22.4R3-S10 custom | Not specified |
| CNA | Juniper Networks | Junos OS | affected 23.2 23.2R2-S7 custom | Not specified |
| CNA | Juniper Networks | Junos OS | affected 23.4 23.4R2-S8 custom | Not specified |
| CNA | Juniper Networks | Junos OS | unaffected 22.3R1 custom | Not specified |
| CNA | Juniper Networks | Junos OS Evolved | affected 23.2 23.2R2-S7-EVO custom | Not specified |
| CNA | Juniper Networks | Junos OS Evolved | affected 23.4 23.4R2-S8-EVO custom | Not specified |
| CNA | Juniper Networks | Junos OS Evolved | unaffected 22.3R1-EVO custom | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/orangecertcc/security-research/security/advisories/GHSA-g4f7-... | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | github.com | |
| supportportal.juniper.net/JSA110072 | [email protected] | supportportal.juniper.net | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Juniper SIRT would like to acknowledge and thank Orange CERT-CC from the Orange group for responsibly reporting this vulnerability. (en)
Additional Advisory Data
Solutions
CNA: The following software releases have been updated to resolve this specific issue: Junos OS: 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8, 24.2R1, and all subsequent releases. Junos OS Evolved: 23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R1-EVO, and all subsequent releases.
Workarounds
CNA: There are no direct workarounds for this issue. One of the following mitigations will prevent malicious exploitation: * Use access lists or firewall filters to limit access to the CLI only from trusted hosts and administrators. * Utilize command authorization to limit the ability to enter config mode to trusted administrators.
Exploits
CNA: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.