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JunosOperating system · Juniper

CVE-2020-1662

HIGH · 7.5 CVSS v3.1 Published 2020-10-16
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable 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
On Juniper Networks Junos OS and Junos OS Evolved devices, BGP session flapping can lead to a routing process daemon (RPD) crash and restart, limiting the attack surface to configured BGP peers. This issue only affects devices with BGP damping in combination with accepted-prefix-limit configuration. When the issue occurs the following messages will appear in the /var/log/messages: rpd[6046]: %DAEMON-4-BGP_PREFIX_THRESH_EXCEEDED: XXXX (External AS x): Configured maximum accepted prefix-limit threshold(1800) exceeded for inet6-unicast nlri: 1984 (instance master) rpd[6046]: %DAEMON-3-BGP_CEASE_PREFIX_LIMIT_EXCEEDED: 2001:x:x:x::2 (External AS x): Shutting down peer due to exceeding configured maximum accepted prefix-limit(2000) for inet6-unicast nlri: 2001 (instance master) rpd[6046]: %DAEMON-4: bgp_rt_maxprefixes_check_common:9284: NOTIFICATION sent to 2001:x:x:x::2 (External AS x): code 6 (Cease) subcode 1 (Maximum Number of Prefixes Reached) AFI: 2 SAFI: 1 prefix limit 2000 kernel: %KERN-5: mastership_relinquish_on_process_exit: RPD crashed on master RE. Sending SIGUSR2 to chassisd (5612:chassisd) to trigger RE switchover This issue affects: Juniper Networks Junos OS: 17.2R3-S3; 17.3 version 17.3R3-S3 and later versions, prior to 17.3R3-S8; 17.4 version 17.4R2-S4, 17.4R3 and later versions, prior to 17.4R2-S10, 17.4R3-S2; 18.1 version 18.1R3-S6 and later versions, prior to 18.1R3-S10; 18.2 version 18.2R3 and later versions, prior to 18.2R3-S4; 18.2X75 version 18.2X75-D50, 18.2X75-D60 and later versions, prior to 18.2X75-D53, 18.2X75-D65; 18.3 version 18.3R2 and later versions, prior to 18.3R2-S4, 18.3R3-S2; 18.4 version 18.4R2 and later versions, prior to 18.4R2-S5, 18.4R3-S2; 19.1 version 19.1R1 and later versions, prior to 19.1R2-S2, 19.1R3-S1; 19.2 version 19.2R1 and later versions, prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2; 20.1 versions prior to 20.1R1-S2, 20.1R2. Juniper Networks Junos OS Evolved prior to 20.1R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 17.2R3-S3.

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

On Juniper Networks Junos OS and Junos OS Evolved, a vulnerability exists where BGP session flapping can cause the routing process daemon (RPD) to crash and restart on devices with both BGP damping and accepted-prefix-limit configuration enabled. When prefix limits are exceeded during flapping, the daemon crashes triggering a RE switchover, resulting in denial of service.

MitigationApply the vendor-supplied software updates for the specific Junos OS versions listed. If immediate patching is not possible, carefully review BGP damping and prefix-limit configurations as a potential workaround, though the only complete remediation is the software update.

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:= 17.2= 17.3= 17.4= 18.1= 18.2= 18.2x75= 18.3= 18.4= 19.1= 19.2= 19.3= 19.4

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

CVSS:3.1/AV:N/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 version
    Run 'show version' or 'systemctl status rpd' to identify the installed Junos OS version
    Affected if The version matches 17.2, 17.3, 17.4, 18.1, 18.2, 18.2x75, 18.3, 18.4, 19.1, 19.2, 19.3, or 19.4
  2. Verify BGP damping configuration
    Run 'show configuration protocols bgp damping' to see if BGP damping is enabled
    Affected if Damping is configured and active under the BGP protocol hierarchy
  3. Verify accepted-prefix-limit configuration
    Run 'show configuration protocols bgp group <group-name> | display set' or inspect the BGP group/neighbor configuration for 'accepted-prefix-limit'
    Affected if An accepted-prefix-limit value is configured under a BGP group or neighbor
  4. Confirm both features are active together
    Review the combined configuration output from steps 2 and 3 to confirm both BGP damping and accepted-prefix-limit exist simultaneously in the configuration
    Affected if Both BGP damping and accepted-prefix-limit are simultaneously configured on the same device

A device is affected if it runs one of the listed vulnerable Junos OS versions AND has both BGP damping and accepted-prefix-limit configured, making it susceptible to RPD crashes during BGP session flapping.

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 for the specific Junos OS versions listed. If immediate patching is not possible, carefully review BGP damping and prefix-limit configurations as a potential workaround, though the only complete remediation is the software update.

Fix this in Junos Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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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-2020-1662 in production — separate from our analysis above.

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What belongs here
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