NULL pointer dereference in Junos OS and Junos OS Evolved - CVE-2026-21901
Published: July 8, 2026
Vulnerability identifier: #VU137138
CSH Severity: Low
CVSS v4: 6.7 [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]
CVE-ID: CVE-2026-21901
CWE-ID: CWE-476
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local privileged user to perform a denial of service (DoS) attack.
The vulnerability exists due to null pointer dereference error in the management daemon (mgd). A local privileged user can 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 1 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.
Affected software
Junos OS
Junos OS Evolved
Junos OS Evolved
How to mitigate CVE-2026-21901
Install updates from vendor's website.
Junos OS - addressed in versions 22.3R3-S5, 22.4R3-S10, 23.2R2-S7, 23.4R2-S8, 24.2R1
Junos OS Evolved - addressed in versions 23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R1-EVO
Junos OS Evolved - addressed in versions 23.2R2-S7-EVO, 23.4R2-S8-EVO, 24.2R1-EVO