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JunosOperating system · Juniper

CVE-2025-59957

MEDIUM · 6.8 CVSS v3.1 Published 2025-10-09
Fix available
A fix is available. Upgrade to 21.4 or later.
See remediation →
73/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Physical access vulnerability in Junos OS on EX4600/QFX5000 Series allows unauthenticated attackers to modify /etc/config/<platform>-defaults[-flex].conf when no root password is set. The modified file contents are silently added to the device configuration, enabling persistent backdoor access that survives reboots and zeroization.

MitigationEnsure root password is configured on all affected devices, upgrade to patched versions (21.4R3+, 22.2R3-S3+), and for compromised devices perform complete reinstallation from physical media - the backdoor survives zeroization.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
JunosOperating system
Affected:< 21.4= 21.4= 22.2

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Physical
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify device model
    Run 'show chassis hardware' or check physical labeling to confirm the device is an EX4600 or QFX5000 series switch
    Affected if Device model is EX4600 or QFX5000 series AND Junos version is < 21.4, = 21.4, or = 22.2
  2. Check Junos OS version
    Run 'show version' or 'show version detail' to obtain the installed Junos OS version
    Affected if Version matches < 21.4, 21.4, or 22.2 (specific builds within these releases)
  3. Verify root password configuration status
    Run 'show system login' or check the configuration for presence of a root authentication method: 'show configuration system login | display set' or 'show configuration system root-authentication'
    Affected if No root password or root authentication is configured (the system has an empty root login or no root password set)
  4. Inspect configuration rollback files
    Examine /etc/config/ directory for any unexpected or recently modified <platform>-defaults.conf or <platform>-defaults-flex.conf files using 'ls -la /etc/config/'
    Affected if Unknown or unauthorized modifications exist in the defaults configuration files

The device is affected if it is an EX4600 or QFX5000 series running Junos < 21.4, 21.4, or 22.2 AND has no root password configured, allowing physical attackers to inject persistent backdoors via /etc/config/ defaults files.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 21.4 or later
Fixed in 21.4
Interim mitigation

Ensure root password is configured on all affected devices, upgrade to patched versions (21.4R3+, 22.2R3-S3+), and for compromised devices perform complete reinstallation from physical media - the backdoor survives zeroization.

Recommended fix High confidence

21.4R3 or later (for versions < 21.4); 22.2R3-S3 or later (for 22.2.x versions)

  1. 1. Identify the current Junos OS version on the EX4600 or QFX5000 Series device using 'show version'
  2. 2. If running a version before 21.4R3, plan upgrade to 21.4R3 or later
  3. 3. If running 22.2.x, plan upgrade to 22.2R3-S3 or later
  4. 4. Ensure you have a valid backup of the current configuration
  5. 5. Download the appropriate fixed Junos OS image from Juniper Networks support portal
  6. 6. Upload the image to the device using 'request system software add <image>' or via USB physical media
  7. 7. Reboot the device using 'request system reboot'
  8. 8. After upgrade, verify the running version with 'show version'
Caveat Junos OS upgrades may introduce configuration syntax changes; review release notes for compatibility alerts before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Junos Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-59957 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data