StarosOperating system · Cisco
CVE-2020-3500
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 · uneditedA vulnerability in the IPv6 implementation of Cisco StarOS could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient validation of incoming IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet to an affected device with the goal of reaching the vulnerable section of the input buffer. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. This vulnerability is specific to IPv6 traffic. IPv4 traffic is not affected.
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 buffer handling vulnerability exists in Cisco StarOS IPv6 packet processing due to insufficient input validation. An attacker can send a specially crafted IPv6 packet to reach a vulnerable input buffer section, triggering a device reload and denial of service. IPv4 traffic is not affected by this vulnerability.
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
StarosOperating system
< 21.18.3CVSS 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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Confirm the device runs Cisco StarOSAccess the device CLI and run 'show version' or 'show os-info' to identify the operating system. StarOS is typically used on Cisco ASR 5000 series, ASR 5500, and virtual platforms.Affected if The device is running Cisco StarOS (not IOS, IOS-XE, NX-OS, or other Cisco OS)
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Determine the installed StarOS versionRun 'show version' or 'show os-info' in the CLI to display the installed StarOS version number.Affected if The displayed StarOS version is lower than 21.18.3 (for example, 21.18.2, 21.17.x, or earlier)
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Verify IPv6 is enabled on the deviceRun 'show ipv6' or 'show ipv6 interface' in the CLI to check if IPv6 processing is configured and active.Affected if IPv6 interfaces or IPv6 processing is enabled on the device
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Confirm IPv6 traffic can reach the deviceReview the device's interface configurations and security policies to determine if untrusted IPv6 packets can be received on any active interface.Affected if IPv6 traffic from untrusted sources can reach the device's input buffers
The device is affected if it runs Cisco StarOS version lower than 21.18.3, has IPv6 enabled, and can receive untrusted IPv6 packets.
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 data21.18.3
Apply Cisco-provided software updates for StarOS when available. As an interim measure, consider filtering or blocking untrusted IPv6 traffic at network boundaries until the patch can be deployed.
Fix this in Staros
Scoped from the published advisory
- Consultation8.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $10,240.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3500 — 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-2020-3500 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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