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StarosOperating system · Cisco

CVE-2018-0239

HIGH · 7.5 CVSS v3.1 Published 2018-04-19
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
A vulnerability in the egress packet processing functionality of the Cisco StarOS operating system for Cisco Aggregation Services Router (ASR) 5700 Series devices and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to cause an interface on the device to cease forwarding packets. The device may need to be manually reloaded to clear this Interface Forwarding Denial of Service condition. The vulnerability is due to the failure to properly check that the length of a packet to transmit does not exceed the maximum supported length of the network interface card (NIC). An attacker could exploit this vulnerability by sending a crafted IP packet or a series of crafted IP fragments through an interface on the targeted device. A successful exploit could allow the attacker to cause the network interface to cease forwarding packets. This vulnerability could be triggered by either IPv4 or IPv6 network traffic. This vulnerability affects the following Cisco products when they are running the StarOS operating system and a virtual interface card is installed on the device: Aggregation Services Router (ASR) 5700 Series, Virtualized Packet Core-Distributed Instance (VPC-DI) System Software, Virtualized Packet Core-Single Instance (VPC-SI) System Software. Cisco Bug IDs: CSCvf32385.

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

A vulnerability in the egress packet processing of Cisco StarOS for ASR 5700 Series and VPC systems allows an unauthenticated remote attacker to cause a network interface to stop forwarding packets by sending crafted IP packets or fragments that exceed the NIC's maximum supported length. The device requires manual reload to recover from this DoS condition. Both IPv4 and IPv6 traffic can trigger the vulnerability.

MitigationApply the vendor patch for Cisco Bug ID CSCvf32385. If immediate patching is not possible, isolate affected systems from untrusted networks using ACLs or firewall rules to reduce attack surface.

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
Affected:= 21.0.v0.65819= 21.0.v4= 21.1.v6= 21.3.1= 21.4.0

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. Identify the device model
    Run 'show hardware' or 'show version' to confirm the system is an ASR 5700 Series or Virtual Packet Core (VPC) system
    Affected if Device is not an ASR 5700 or VPC system - this vulnerability only affects those platforms
  2. Confirm StarOS is running
    Run 'show system' or 'show version' to verify the operating system is Cisco StarOS
    Affected if The device does not run StarOS - this vulnerability is specific to StarOS
  3. Check the StarOS version
    Run 'show version' or 'show build' to obtain the StarOS build version, then compare it against the affected versions: 21.0.v0.65819, 21.0.v4, 21.1.v6, 21.3.1, or 21.4.0
    Affected if The installed StarOS version exactly matches one of the listed affected versions (note: version format uses 'v' as delimiter)
  4. Verify egress packet processing is active
    Run 'show interface' to confirm at least one network interface is configured and operational for egress traffic
    Affected if No interfaces are configured - however, most ASR 5700/VPC deployments will have active interfaces by default

The system is affected only if it is an ASR 5700 or VPC device running StarOS with a version exactly matching 21.0.v0.65819, 21.0.v4, 21.1.v6, 21.3.1, or 21.4.0, and has active network interfaces.

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 patch for Cisco Bug ID CSCvf32385. If immediate patching is not possible, isolate affected systems from untrusted networks using ACLs or firewall rules to reduce attack surface.

Fix this in Staros Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2018-0239 in production — separate from our analysis above.

No notes yet

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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
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data