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Junos Os EvolvedOperating system · Juniper

CVE-2021-0209

MEDIUM · 6.5 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 →
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
In Juniper Networks Junos OS Evolved an attacker sending certain valid BGP update packets may cause Junos OS Evolved to access an uninitialized pointer causing RPD to core leading to a Denial of Service (DoS). Continued receipt of these types of valid BGP update packets will cause an extended Denial of Service condition. RPD will require a restart to recover. An indicator of compromise is to see if the file rpd.re exists by issuing the command: show system core-dumps This issue affects: Juniper Networks Junos OS Evolved 19.4 versions prior to 19.4R2-S2-EVO; 20.1 versions prior to 20.1R1-S2-EVO, 20.1R2-S1-EVO. This issue does not affect Junos OS.

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 Juniper Networks Junos OS Evolved, processing certain valid BGP update packets triggers an uninitialized pointer access in the routing daemon (RPD), causing it to crash and core dump. This results in a denial of service that persists until RPD is manually restarted. The vulnerability is triggered specifically by malformed but technically valid BGP update messages.

MitigationUpgrade Junos OS Evolved to version 19.4R2-S2-EVO or later, or 20.1R2-S1-EVO or later. Monitor for RPD crashes by checking for rpd.re core dump files using 'show system core-dumps'.

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

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. Check Junos OS Evolved version
    Run 'show version' or 'show system information' to display the installed Junos OS Evolved version
    Affected if The version is 19.4 (any build) or 20.1 (any build) without being a fixed release like 19.4R2-S2-EVO or 20.1R2-S1-EVO or later
  2. Verify BGP is configured
    Run 'show configuration protocols bgp' to check if BGP is actively configured on the device
    Affected if BGP is configured and accepting peer connections, making the device potentially reachable to malformed BGP updates
  3. Check for existing RPD core dumps
    Run 'show system core-dumps' to list any core dump files, specifically looking for rpd.re core files
    Affected if An rpd.re core dump file exists, indicating RPD has crashed due to this vulnerability
  4. Verify RPD process stability
    Run 'show system processes rpd' or check process uptime to determine if RPD is currently running normally
    Affected if RPD is not running or has recently restarted, suggesting a crash from which it required manual intervention to recover
  5. Review system logs for RPD crashes
    Run 'show log messages' or 'show log daemon' and search for RPD crash indicators or core dump generation events
    Affected if Logs contain recent RPD crash entries or references to rpd.re core dumps with timestamps corresponding to BGP update receipt

A user is affected if they run Junos OS Evolved versions 19.4 or 20.1, have BGP configured, and either have existing rpd.re core dumps or are experiencing RPD instability.

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 Evolved to version 19.4R2-S2-EVO or later, or 20.1R2-S1-EVO or later. Monitor for RPD crashes by checking for rpd.re core dump files using 'show system core-dumps'.

Fix this in Junos Os Evolved Scoped from the published advisory
  • Consultation4.0 h
  • Implementation3.0 h
  • Testing4.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,300
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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-2021-0209 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
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  • Version or environment caveats, and links to real fixes
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