CVE-2020-1686
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 · uneditedOn Juniper Networks Junos OS devices, receipt of a malformed IPv6 packet may cause the system to crash and restart (vmcore). This issue can be trigged by a malformed IPv6 packet destined to the Routing Engine. An attacker can repeatedly send the offending packet resulting in an extended Denial of Service condition. Only IPv6 packets can trigger this issue. IPv4 packets cannot trigger this issue. This issue affects Juniper Networks Junos OS 18.4 versions prior to 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S4, 19.3R3; 19.4 versions prior to 19.4R1-S3, 19.4R2. This issue does not affect Juniper Networks Junos OS prior to 18.4R1.
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 denial of service vulnerability in Juniper Junos OS allows remote attackers to crash and restart affected devices by sending malformed IPv6 packets to the Routing Engine. Repeated exploitation can cause extended DoS conditions. Only IPv6 traffic can trigger this issue; IPv4 is not affected.
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= 18.4= 19.1= 19.2= 19.3= 19.4CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Identify installed Junos OS versionRun 'show version' on the device CLI to display the installed Junos OS releaseAffected if The version matches one of the affected releases: 18.4, 19.1, 19.2, 19.3, or 19.4 (specific minor versions within these releases)
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Check IPv6 interface statusRun 'show ipv6 interface' to list active IPv6 interfaces on the deviceAffected if IPv6 interfaces are listed as UP and active (the vulnerability is triggered only by IPv6 traffic)
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Confirm IPv6 routing configurationReview the routing configuration using 'show configuration routing-options' or check for inet6 family settingsAffected if IPv6 routing is enabled or inet6 protocols are configured, meaning the device processes IPv6 packets destined for the Routing Engine
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Assess IPv6 network exposureExamine interface configurations and firewall policies to determine if the device accepts IPv6 traffic from network segments where malformed packets could originateAffected if The device has reachable IPv6 addresses from untrusted or external networks
The device is affected if it runs an affected Junos version (18.4 through 19.4) AND has IPv6 enabled and reachable, allowing malformed IPv6 packets to reach the Routing Engine.
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 vendor-supplied patches for Junos OS versions 18.4R2-S4 and later, 18.4R3-S1, 19.1R2-S1 and later, 19.1R3, 19.2R1-S5 and later, 19.2R2, 19.3R2-S4 and later, 19.3R3, 19.4R1-S3 and later, and 19.4R2. Consider filtering malformed IPv6 packets at network boundaries as a temporary mitigation.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-1686 — 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-2020-1686 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
No notes yet
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- Version or environment caveats, and links to real fixes
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