CVE-2026-21901
Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash
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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Junos OS and Junos OS Evolved: Configuration of a specific SSH option results in mgd crash
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.
- Record
CVE-2026-21901- CVSS 4.0
- 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/AU:Y/R:A/V:D/RE:M/U:Green - CVSS 3.1
- 4.4 Medium
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-476
- Updated
- 2026-11-02
EUVDEUVD-2026-42697
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.
- Record
EUVD-2026-42697- CVSS 4.0
- 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/AU:Y/R:A/V:D/RE:M/U:Green - Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-21901- CVSS 4.0
- 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 - CVSS 3.1
- 4.4 Medium
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-476
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-21901 is a medium vulnerability (CVSS 6.7) in Juniper Junos, published July 9, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.18%, the 7th percentile. No source names a fixed version.