CVE-2025-59957: An Origin Validation Error vulnerability in an insufficient protected file of Juniper Networks Junos OS on EX4600 Series and QFX5000 Series allows an ...

Description

An Origin Validation Error vulnerability in an insufficient protected file of Juniper Networks Junos OS on EX4600 Series and QFX5000 Series allows an unauthenticated attacker with physical access to the device to create a backdoor which allows complete control of the system. When a device isn't configured with a root password, an attacker can modify a specific file. It's contents will be added to the Junos configuration of the device without being visible. This allows for the addition of any configuration unknown to the actual operator, which includes users, IP addresses and other configuration which could allow unauthorized access to the device. This exploit is persistent across reboots and even zeroization. The indicator of compromise is a modified /etc/config/<platform>-defaults[-flex].conf file. Review that file for unexpected configuration statements, or compare it to an unmodified version which can be extracted from the original Juniper software image file. For details on the extraction procedure please contact Juniper Technical Assistance Center (JTAC). To restore the device to a trusted initial configuration the system needs to be reinstalled from physical media. This issue affects Junos OS on EX4600 Series and QFX5000 Series: * All versions before 21.4R3, * 22.2 versions before 22.2R3-S3.

Metrics

CVSS 3.1

6.8/10

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS 4.0

7/10

CVSS:4.0/AV:P/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/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:N/R:U/V:X/RE:H/U:X

EPSS Probability

0.17%

6.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-346

Affected Software

Vendor	Product	Versions
Juniper	Junos	< 21.4
Juniper	Junos	21.4
Juniper	Junos	22.2

References

https://support.juniper.net/support/requesting-support/Vendor Advisory
https://supportportal.juniper.net/JSA103146Vendor Advisory
https://supportportal.juniper.net/s/article/EX-QFX-Procedure-to-format-install-QFX5K-device-using-a-USBTechnical Description

Timeline

Published: Oct 9, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-59957?

An Origin Validation Error vulnerability in an insufficient protected file of Juniper Networks Junos OS on EX4600 Series and QFX5000 Series allows an unauthenticated attacker with physical access to the device to create a backdoor which allows complete control of the system. When a device isn't configured with a root password, an attacker can modify a specific file. It's contents will be added to the Junos configuration of the device without being visible. This allows for the addition of any configuration unknown to the actual operator, which includes users, IP addresses and other configuration which could allow unauthorized access to the device. This exploit is persistent across reboots and even zeroization. The indicator of compromise is a modified /etc/config/<platform>-defaults[-flex].conf file. Review that file for unexpected configuration statements, or compare it to an unmodified version which can be extracted from the original Juniper software image file. For details on the extraction procedure please contact Juniper Technical Assistance Center (JTAC). To restore the device to a trusted initial configuration the system needs to be reinstalled from physical media. This issue affects Junos OS on EX4600 Series and QFX5000 Series: * All versions before 21.4R3, * 22.2 versions before 22.2R3-S3.

How severe is CVE-2025-59957?

CVE-2025-59957 has a CVSS score of 7/10 (HIGH severity). The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2025-59957?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.