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JunosOperating system · Juniper

CVE-2021-0231

MEDIUM · 6.5 CVSS v3.1 Published 2021-04-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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
A path traversal vulnerability in the Juniper Networks SRX and vSRX Series may allow an authenticated J-web user to read sensitive system files. This issue affects Juniper Networks Junos OS on SRX and vSRX Series: 19.3 versions prior to 19.3R2-S6, 19.3R3-S1; 19.4 versions prior to 19.4R2-S4, 19.4R3; 20.1 versions prior to 20.1R1-S4, 20.1R2; 20.2 versions prior to 20.2R1-S3, 20.2R2; This issue does not affect Juniper Networks Junos OS versions prior to 19.3R1.

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

Path traversal vulnerability in the J-web management interface of Juniper SRX and vSRX Series allows authenticated users to manipulate file path references to read sensitive system files outside the intended web root directory.

MitigationUpgrade Junos OS to the specified fixed versions (19.3R2-S6/19.3R3-S1, 19.4R2-S4/19.4R3, 20.1R1-S4/20.1R2, 20.2R1-S3/20.2R2 or later). Additionally, restrict J-web access to trusted management networks and disable J-web if not required.

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:= 19.3= 19.4= 20.1= 20.2

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

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

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 and platform type
    Run 'show version' or check the device model to confirm it is an SRX Series or vSRX virtual appliance. This vulnerability only affects those specific product lines.
    Affected if Device is an SRX or vSRX Series
  2. Check if J-web management interface is enabled
    Review the system services configuration by running 'show configuration system services web-management' or checking the configuration for 'system services web-management' hierarchy. J-web must be enabled for this vulnerability to be exploitable.
    Affected if J-web management interface is enabled and accessible
  3. Determine installed Junos OS version
    Run 'show version' or 'show system software' to obtain the exact Junos OS version installed on the device.
    Affected if Installed version is 19.3, 19.4, 20.1, or 20.2 (any release within these branches)
  4. Compare version against affected ranges
    Match the installed Junos version against the affected versions: 19.3, 19.4, 20.1, 20.2. Any version within these branches is considered affected if J-web is enabled.
    Affected if Version falls within 19.3, 19.4, 20.1, or 20.2 branches and J-web is active
  5. Verify management access method
    Confirm whether J-web is accessible from untrusted networks by reviewing firewall policies, interface bindings, and the 'system services web-management http' or 'https' configuration with its interface restrictions.
    Affected if J-web is reachable from management networks that are not explicitly trusted

The environment is affected if the device is an SRX or vSRX running Junos 19.3, 19.4, 20.1, or 20.2 with J-web management interface enabled and accessible.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Junos OS to the specified fixed versions (19.3R2-S6/19.3R3-S1, 19.4R2-S4/19.4R3, 20.1R1-S4/20.1R2, 20.2R1-S3/20.2R2 or later). Additionally, restrict J-web access to trusted management networks and disable J-web if not required.

Fix this in Junos Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
27.0 hours of engineering $4,800
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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-2021-0231 in production — separate from our analysis above.

No notes yet

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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