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JunosOperating system · Juniper

CVE-2021-0248

CRITICAL · 10.0 CVSS v3.1 Published 2021-04-22
Fix available
A fix is available. Upgrade to 19.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable 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
This issue is not applicable to NFX NextGen Software. On NFX Series devices the use of Hard-coded Credentials in Juniper Networks Junos OS allows an attacker to take over any instance of an NFX deployment. This issue is only exploitable through administrative interfaces. This issue affects: Juniper Networks Junos OS versions prior to 19.1R1 on NFX Series. No other platforms besides NFX Series devices are affected.

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

Hard-coded credentials in Juniper Networks Junos OS on NFX Series devices allow an unauthenticated attacker with access to administrative interfaces to take complete control of the device. The vulnerability exists in versions prior to 19.1R1 and is specific to NFX Series platforms only, representing a critical authentication bypass.

MitigationUpgrade Junos OS on NFX Series devices to version 19.1R1 or later to remove the hardcoded credentials. Restrict administrative interface access until the upgrade is completed.

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:< 19.1= 19.1

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 platform
    Check the hardware model or product name of the Juniper device (typically via 'show chassis hardware' or 'show system information' command)
    Affected if The device is NOT an NFX Series platform - if it is a different Juniper product line, this CVE does not apply
  2. Check Junos OS version
    Run 'show version' or 'show system information' to retrieve the installed Junos OS version number
    Affected if The installed version is prior to 19.1R1 (such as 18.x, 19.0) or exactly 19.1 - these versions contain the hard-coded credentials on NFX Series devices
  3. Verify administrative interface exposure
    Review network configuration for exposed management interfaces (HTTP, HTTPS, SSH, telnet) on the device - check 'show configuration system services'
    Affected if Administrative interfaces (web UI, CLI over SSH/telnet) are accessible to the attacker - the vulnerability requires the attacker to reach these interfaces to use the hard-coded credentials

The environment is affected if it is an NFX Series device running Junos OS version 19.1 or any version prior to 19.1R1, and administrative interfaces are network-accessible to the attacker.

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 19.1 or later
Fixed in 19.1
Interim mitigation

Upgrade Junos OS on NFX Series devices to version 19.1R1 or later to remove the hardcoded credentials. Restrict administrative interface access until the upgrade is completed.

Recommended fix High confidence

19.1R1 or later (Junos OS 19.1R1 is the first fixed release)

  1. Identify the current Junos OS version running on the NFX Series device using 'show version' command
  2. Obtain Junos OS 19.1R1 or later from the Juniper Networks support portal (https://www.juniper.net/customers/csc//)
  3. Review Juniper upgrade documentation for NFX Series devices to understand the upgrade procedure
  4. Back up the current device configuration using 'request system configuration archive' or 'save' command
  5. Transfer the new Junos OS image to the device
  6. Initiate the software installation using 'request system software add <package-name>' command
  7. Reboot the device if required by the upgrade process
  8. Verify the new version is installed using 'show version' and confirm it shows 19.1R1 or later

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

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,840
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.

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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-2021-0248 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