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Junos Os EvolvedOperating system · Juniper

CVE-2021-0292

MEDIUM · 6.5 CVSS v3.1 Published 2021-07-15
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
An Uncontrolled Resource Consumption vulnerability in the ARP daemon (arpd) and Network Discovery Protocol (ndp) process of Juniper Networks Junos OS Evolved allows a malicious attacker on the local network to consume memory resources, ultimately resulting in a Denial of Service (DoS) condition. Link-layer functions such as IPv4 and/or IPv6 address resolution may be impacted, leading to traffic loss. The processes do not recover on their own and must be manually restarted. Changes in memory usage can be monitored using the following shell commands (header shown for clarity): user@router:/var/log# ps aux | grep arpd USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 31418 59.0 0.7 *5702564* 247952 ? xxx /usr/sbin/arpd --app-name arpd -I object_select --shared-objects-mode 3 user@router:/var/log# ps aux | grep arpd USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 31418 49.1 1.0 *5813156* 351184 ? xxx /usr/sbin/arpd --app-name arpd -I object_select --shared-objects-mode 3 Memory usage can be monitored for the ndp process in a similar fashion: user@router:/var/log# ps aux | grep ndp USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 14935 0.0 0.1 *5614052* 27256 ? Ssl Jun15 0:17 /usr/sbin/ndp -I no_tab_chk,object_select --app-name ndp --shared-obje user@router:/var/log# ps aux | grep ndp USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 14935 0.0 0.1 *5725164* 27256 ? Ssl Jun15 0:17 /usr/sbin/ndp -I no_tab_chk,object_select --app-name ndp --shared-obje This issue affects Juniper Networks Junos OS Evolved: 19.4 versions prior to 19.4R2-S3-EVO; 20.1 versions prior to 20.1R2-S4-EVO; all versions of 20.2-EVO. This issue does not affect Juniper Networks Junos OS Evolved versions prior to 19.4R2-EVO.

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

A memory consumption vulnerability exists in the ARP daemon (arpd) and Network Discovery Protocol (ndp) processes in Juniper Networks Junos OS Evolved. An attacker on the local network can send specially crafted packets that cause unbounded memory growth in these processes, ultimately exhausting resources and causing a Denial of Service. The affected processes do not self-recover and require manual restart.

MitigationApply the vendor-supplied software updates (19.4R2-S3-EVO, 20.1R2-S4-EVO, or later) to address the uncontrolled resource consumption. Monitor process memory usage using the documented ps commands and restart affected processes (arpd, ndp) manually until the fix can be deployed.

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
Junos Os EvolvedOperating system
Affected:= 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
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. Verify Junos OS Evolved is running
    Run 'show version' or 'show system information' and look for 'Junos OS Evolved' in the output (not plain Junos OS)
    Affected if System is running Junos OS Evolved (the vulnerability only affects Evolved, not standard Junos OS)
  2. Check installed version against affected ranges
    Run 'show version' and locate the Junos OS version number; compare against affected versions 19.4, 20.1, and 20.2 (all point releases within these trains)
    Affected if Version begins with 19.4, 20.1, or 20.2 (any sub-version like 20.2R1, 20.2R2, etc.)
  3. Confirm arpd process is running
    Run 'show system processes extensive | match arpd' or 'ps -aux | grep arpd' to verify the arpd daemon is active
    Affected if arpd process is running (the vulnerability affects this process specifically)
  4. Confirm ndp process is running
    Run 'show system processes extensive | match ndp' or 'ps -aux | grep ndp' to verify the ndp daemon is active
    Affected if ndp process is running (the vulnerability affects this process specifically)
  5. Monitor memory consumption of affected processes
    Run 'show system processes process-name arpd' and 'show system processes process-name ndp' repeatedly over time, or use 'ps -o pid,vsz,rss,comm -p $(pgrep -f arpd)' to observe memory growth
    Affected if Memory usage of arpd or ndp shows continuous unbounded growth without stabilizing

You are affected if running Junos OS Evolved versions 19.4, 20.1, or 20.2 with either the arpd or ndp process active, and you observe abnormal memory growth in those processes.

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 vendor-supplied software updates (19.4R2-S3-EVO, 20.1R2-S4-EVO, or later) to address the uncontrolled resource consumption. Monitor process memory usage using the documented ps commands and restart affected processes (arpd, ndp) manually until the fix can be deployed.

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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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-2021-0292 in production — separate from our analysis above.

No notes yet

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What this is

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What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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