CVE-2020-1632
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 · uneditedIn a certain condition, receipt of a specific BGP UPDATE message might cause Juniper Networks Junos OS and Junos OS Evolved devices to advertise an invalid BGP UPDATE message to other peers, causing the other peers to terminate the established BGP session, creating a Denial of Service (DoS) condition. For example, Router A sends a specific BGP UPDATE to Router B, causing Router B to send an invalid BGP UPDATE message to Router C, resulting in termination of the BGP session between Router B and Router C. This issue might occur when there is at least a single BGP session established on the device that does not support 4 Byte AS extension (RFC 4893). Repeated receipt of the same BGP UPDATE can result in an extended DoS condition. This issue affects Juniper Networks Junos OS: 16.1 versions prior to 16.1R7-S6; 16.2 versions prior to 16.2R2-S11; 17.1 versions prior to 17.1R2-S11, 17.1R3-S2; 17.2 versions prior to 17.2R1-S9, 17.2R2-S8, 17.2R3-S3; 17.2X75 versions prior to 17.2X75-D105, 17.2X75-D110, 17.2X75-D44; 17.3 versions prior to 17.3R2-S5, 17.3R3-S7; 17.4 versions prior to 17.4R2-S8, 17.4R3; 18.1 versions prior to 18.1R3-S8; 18.2 versions prior to 18.2R2-S6, 18.2R3-S2; 18.2X75 versions prior to 18.2X75-D12, 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D51, 18.2X75-D60; 18.3 versions prior to 18.3R1-S6, 18.3R2-S3, 18.3R3; 18.4 versions prior to 18.4R1-S5, 18.4R3; 18.4 version 18.4R2 and later versions; 19.1 versions prior to 19.1R1-S3, 19.1R2; 19.2 versions prior to 19.2R1-S2, 19.2R2. This issue does not affect Juniper Networks Junos OS prior to 16.1R1. This issue affects Juniper Networks Junos OS Evolved prior to 19.2R2-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 confidenceA vulnerability in Juniper Networks Junos OS and Junos OS Evolved allows a specially crafted BGP UPDATE message to cause the device to generate and advertise an invalid BGP UPDATE to other peers, terminating BGP sessions and creating a DoS condition. The issue occurs specifically when the device has at least one BGP peer that does not support the 4 Byte AS extension (RFC 4893).
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= 16.1= 16.2= 17.1= 17.2= 17.2x75= 17.3= 17.4= 18.1= 18.1x75= 18.3= 18.4= 19.1= 19.2CVSS 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
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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 checksWork through these to decide whether this CVE applies to you.
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Check Junos OS versionExecute 'show version' or 'request system software version' on the device CLIAffected if The displayed version matches any of the affected versions: 16.1, 16.2, 17.1, 17.2, 17.2x75, 17.3, 17.4, 18.1, 18.1x75, 18.3, 18.4, 19.1 (for Junos) or 19.2 (for Junos OS Evolved)
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Identify configured BGP peersExecute 'show bgp summary' to list all configured BGP neighbors and their AS numbersAffected if Any BGP peers are configured on the device
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Check BGP peer 4-byte AS capabilityExecute 'show bgp neighbor' and examine the 'AS4 capability' or 'Four-byte AS' field for each peerAffected if At least one BGP peer does NOT advertise support for 4-byte AS (RFC 4893) - the peer will show no AS4 capability or will be using a 2-byte AS only
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Verify peer AS number sizeCompare the peer AS number from 'show bgp summary' - if any peer AS is >= 65536, it requires 4-byte AS supportAffected if There are peers with AS numbers in the 4-byte range (65536 or higher) but the device also has peers that do not advertise 4-byte AS capability, creating a mixed environment
You are affected if your device runs an affected Junos version AND has at least one BGP peer that does not support 4-byte AS (RFC 4893), creating a mixed peer environment where the vulnerability can be triggered.
Generated from the published advisory. Verify against your own configuration.
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 dataApply the appropriate Junos OS or Junos OS Evolved software update from the vendor (16.1R7-S6, 16.2R2-S11, 17.1R2-S11, 17.1R3-S2, 17.2R1-S9, 17.2R2-S8, 17.2R3-S3, 17.2X75-D105, 17.2X75-D110, 17.2X75-D44, 17.3R2-S5, 17.3R3-S7, 17.4R2-S8, 17.4R3, 18.1R3-S8, 18.2R2-S6, 18.2R3-S2, 18.2X75-D12, 18.2X75-D33, 18.2X75-D411, 18.2X75-D420, 18.2X75-D51, 18.2X75-D60, 18.3R1-S6, 18.3R2-S3, 18.3R3, 18.4R1-S5, 18.4R3, 19.1R1-S3, 19.1R2, 19.2R1-S2, 19.2R2, or 19.2R2-EVO or later). Ensure all BGP peers support 4 Byte AS to reduce attack surface.
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- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-1632 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-1632 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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