CVE-2025-59957 Junos OS: EX4600 Series and QFX5000 Series: An attacker with physical access can open a persistent backdoor
An attacker with physical access can modify a configuration file to create a persistent backdoor, gaining complete control of the device.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-59957?
CVE-2025-59957 is a high-severity authentication bypass vulnerability in Juniper Junos, published on 9 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-346
Which versions are affected by CVE-2025-59957?
It affects 1 product.
Products include Juniper Junos.
How do I fix CVE-2025-59957?
No fix has been published for CVE-2025-59957 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2025-59957 being exploited?
There is no known exploitation of CVE-2025-59957 in the wild and no public exploit code.
Other vulnerabilities in Juniper Junos
- CVE-2023-36845 Juniper Junos OS EX Series and SRX Series PHP External Variable Modification
- CVE-2020-1631 Juniper Junos OS Path Traversal
- CVE-2025-21590 Juniper Junos OS Improper Isolation or Compartmentalization
- CVE-2023-36851 Juniper Junos OS SRX Series Missing Authentication for Critical Function
- CVE-2023-36844 Juniper Junos OS EX Series PHP External Variable Modification
Sources
Also known as GHSA-f6j3-wrc2-m228.