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JunosOperating system · Juniper

CVE-2021-0210

MEDIUM · 6.8 CVSS v3.1 Published 2021-01-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
75/100
Remediation priority · High
Remotely reachable No privileges

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 Information Exposure vulnerability in J-Web of Juniper Networks Junos OS allows an unauthenticated attacker to elevate their privileges over the target system through opportunistic use of an authenticated users session. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S17; 17.3 versions prior to 17.3R3-S10; 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.3 versions prior to 18.3R2-S4, 18.3R3-S4; 18.4 versions prior to 18.4R2-S5, 18.4R3-S5; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S3; 19.2 versions prior to 19.2R1-S5, 19.2R3, 19.2R3-S1; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2-S2, 19.4R3; 20.1 versions prior to 20.1R1-S4, 20.1R2; 20.2 versions prior to 20.2R1-S1, 20.2R2.

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

An information exposure vulnerability in J-Web allows an unauthenticated attacker to hijack or opportunistically use an authenticated user's session to elevate privileges on Juniper Networks Junos OS devices.

MitigationApply the appropriate Junos OS patch from the vendor advisories (12.3R12-S17, 17.3R3-S10, 17.4R2-S12, 18.1R3-S11, 18.2R3-S6, 18.3R2-S4, 18.4R2-S5, 19.1R1-S6, 19.2R1-S5, 19.3R2-S4, 19.4R1-S3, 20.1R1-S4, or later per branch), or 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:= 12.3= 17.3= 17.4= 18.1= 18.2= 18.3= 18.4= 19.1= 19.2= 19.3= 19.4= 20.1

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
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/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 the Junos OS version
    Run 'show version' on the device CLI to obtain the installed Junos version
    Affected if The version matches any of the following branches: 12.3, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4, or 20.1 (any Sx sub-version within these branches)
  2. Confirm J-Web is enabled
    Run 'show system services' or check the configuration under 'set system services web-management' to determine if J-Web is enabled
    Affected if J-Web (web-management) service is configured and active on the device
  3. Verify J-Web HTTP/HTTPS listener
    Check for open ports associated with J-Web (typically 443 or 8080) using 'show system connections' or by attempting to reach the J-Web login page over the network
    Affected if The device is reachable on J-Web ports and the service is responding
  4. Review active sessions
    Use 'show system session' or similar command to review active administrative sessions
    Affected if Multiple concurrent sessions exist, which could indicate session hijacking risk

The device is affected if it runs a Junos version matching the affected branches (12.3, 17.x, 18.x, 19.x, 20.1) AND has J-Web web-management service 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

Apply the appropriate Junos OS patch from the vendor advisories (12.3R12-S17, 17.3R3-S10, 17.4R2-S12, 18.1R3-S11, 18.2R3-S6, 18.3R2-S4, 18.4R2-S5, 19.1R1-S6, 19.2R1-S5, 19.3R2-S4, 19.4R1-S3, 20.1R1-S4, or later per branch), or disable J-Web if not required.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-0210 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