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JunosOperating system · Juniper

CVE-2018-0063

MEDIUM · 6.5 CVSS v3.1 Published 2018-10-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
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
A vulnerability in the IP next-hop index database in Junos OS 17.3R3 may allow a flood of ARP requests, sent to the management interface, to exhaust the private Internal routing interfaces (IRIs) next-hop limit. Once the IRI next-hop database is full, no further next hops can be learned and existing entries cannot be cleared, leading to a sustained denial of service (DoS) condition. An indicator of compromise for this issue is the report of the following error message: %KERN-4: Nexthop index allocation failed: private index space exhausted This issue only affects the management interface, and does not impact regular transit traffic through the FPCs. This issue also only affects Junos OS 17.3R3. No prior versions of Junos OS are affected by this issue. Affected releases are Juniper Networks Junos OS: 17.3R3.

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

In Junos OS 17.3R3, a vulnerability in the IP next-hop index database allows a flood of ARP requests sent to the management interface to exhaust the private Internal Routing Interfaces (IRI) next-hop limit. Once the IRI next-hop database is full, no further next hops can be learned and existing entries cannot be cleared, causing a sustained denial of service. The indicator of compromise is the error message '%KERN-4: Nexthop index allocation failed: private index space exhausted'. This only affects the management interface and does not impact regular transit traffic.

MitigationUpgrade from Junos OS 17.3R3 to a fixed release. As a defensive measure, implement rate-limiting on the management interface to reduce ARP request volume.

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:= 17.3

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 the Junos OS version
    Run 'show version' or 'show version detail' to confirm the exact Junos OS version running on the device
    Affected if The device is running exactly Junos OS 17.3R3 (version 17.3)
  2. Search system logs for the indicator of compromise
    Review system logs (using 'show log messages' or 'show log kernel') for the error message '%KERN-4: Nexthop index allocation failed: private index space exhausted'
    Affected if The error message is present in the logs, indicating the next-hop database has been exhausted
  3. Verify management interface is receiving ARP traffic
    Use 'show interfaces' statistics for the management interface (fxp0 or em0) and monitor ARP request volume with 'show arp' or traffic monitoring tools
    Affected if The management interface is receiving unusually high volumes of ARP requests that could exhaust the IRI next-hop limit
  4. Check next-hop database utilization
    Run 'show system statistics next-hop' or equivalent command to examine the private IRI next-hop index space usage
    Affected if The private next-hop index space shows as exhausted or near exhaustion (100% utilization)
  5. Confirm management interface is still functional
    Attempt to access the device via the management interface and verify responsiveness
    Affected if The management interface is unresponsive or experiencing sustained denial of service despite the device otherwise functioning normally

A device is affected if it is running Junos OS 17.3R3 and exhibits the specific kernel error message indicating the private IRI next-hop index space has been exhausted due to ARP request flooding on the management interface.

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 from Junos OS 17.3R3 to a fixed release. As a defensive measure, implement rate-limiting on the management interface to reduce ARP request volume.

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-2018-0063 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
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