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JunosOperating system · Juniper

CVE-2018-0021

HIGH · 8.8 CVSS v3.0 Published 2018-04-11
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
93/100
Remediation priority · Urgent
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
If all 64 digits of the connectivity association name (CKN) key or all 32 digits of the connectivity association key (CAK) key are not configured, all remaining digits will be auto-configured to 0. Hence, Juniper devices configured with short MacSec keys are at risk to an increased likelihood that an attacker will discover the secret passphrases configured for these keys through dictionary-based and brute-force-based attacks using spoofed packets. Affected releases are Juniper Networks Junos OS: 14.1 versions prior to 14.1R10, 14.1R9; 14.1X53 versions prior to 14.1X53-D47; 15.1 versions prior to 15.1R4-S9, 15.1R6-S6, 15.1R7; 15.1X49 versions prior to 15.1X49-D100; 15.1X53 versions prior to 15.1X53-D59; 16.1 versions prior to 16.1R3-S8, 16.1R4-S8, 16.1R5; 16.2 versions prior to 16.2R1-S6, 16.2R2; 17.1 versions prior to 17.1R2.

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

Juniper devices running affected Junos OS versions auto-populate unspecified digits of MacSec CKN (64-digit) and CAK (32-digit) keys with zeros. When administrators configure short keys, the remaining digits become all zeros, significantly reducing the keyspace and enabling dictionary and brute-force attacks to recover the configured passphrase.

MitigationConfigure full-length MacSec keys (64 hex digits for CKN, 32 hex digits for CAK) on all affected devices, or upgrade to a patched Junos OS version.

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:= 15.1x49= 14.1= 14.1x53= 15.1x53= 16.1= 16.2= 17.1= 15.1

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

CVSS:3.0/AV:A/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 Junos OS version
    Run 'show version' or 'show system information' to obtain the installed Junos OS version
    Affected if Version matches 15.1x49, 14.1, 14.1x53, 15.1x53, 16.1, 16.2, 17.1, or 15.1
  2. Confirm MacSec is configured
    Run 'show security macsec connectivity-association' or inspect the configuration under 'security macsec' hierarchy
    Affected if MacSec connectivity-association exists with CKN or CAK configured
  3. Verify CKN key length
    Run 'show security macsec connectivity-association detail' or view the configured CKN under 'set security macsec connectivity-association <name> ckn' - count the hex digits
    Affected if CKN is configured with fewer than 64 hex digits (leading zeros are auto-padded, reducing effective keyspace)
  4. Verify CAK key length
    Run 'show security macsec connectivity-association detail' or view the configured CAK under 'set security macsec connectivity-association <name> cak' - count the hex digits
    Affected if CAK is configured with fewer than 32 hex digits (leading zeros are auto-padded, reducing effective keyspace)

Device is affected if running any listed Junos version AND MacSec is enabled with CKN shorter than 64 hex digits or CAK shorter than 32 hex digits, because unspecified digits are auto-populated with zeros.

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

Configure full-length MacSec keys (64 hex digits for CKN, 32 hex digits for CAK) on all affected devices, or upgrade to a patched Junos OS version.

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-2018-0021 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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