CVE-2025-21590
Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability
Juniper Junos OS
An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to compromise the integrity of the device. A local attacker with access to the shell is able to inject arbitrary code which can compromise an affected device. This issue is not exploitable from the Junos CLI. This issue affects Junos OS: * All versions before 21.2R3-S9, * 21.4 versions before 21.4R3-S10, * 22.2 versions before 22.2R3-S6, * 22.4 versions before 22.4R3-S6, * 23.2 versions before 23.2R2-S3, * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R1-S2, 24.2R2.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 13 March 2025. US federal agencies were required to remediate it by 3 April 2025.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 1.7%, which is higher than 78% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
Frequently asked questions
Is CVE-2025-21590 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2025-21590.
What does CVE-2025-21590 affect?
CVE-2025-21590 affects Juniper Junos OS. An Improper Isolation or Compartmentalization vulnerability in the kernel of Juniper Networks Junos OS allows a local attacker with high privileges to compromise the integrity of the device. A local attacker with access to the shell is able to inject arbitrary code which can compromise an affected device. This issue is not exploitable from the Junos CLI. This issue affects Junos OS: * All versions before 21.2R3-S9, * 21.4 versions before 21.4R3-S10, * 22.2 versions before 22.2R3-S6, * 22.4 versions before 22.4R3-S6, * 23.2 versions before 23.2R2-S3, * 23.4 versions before 23.4R2-S4, * 24.2 versions before 24.2R1-S2, 24.2R2.
How severe is CVE-2025-21590?
CVE-2025-21590 is rated MEDIUM with a CVSS base score of 4.4. EPSS puts the probability of exploitation in the next 30 days at 1.7%, higher than 78% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 3 April 2025.
How should organisations respond to CVE-2025-21590?
Apply the vendor patch for Juniper Junos OS as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.