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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 17 Mar 2022.
Ios XeOperating system · Cisco

CVE-2018-0151

CRITICAL · 9.8 CVSS v3.1 Published 2018-03-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
In the wild 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 quality of service (QoS) subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition or execute arbitrary code with elevated privileges. The vulnerability is due to incorrect bounds checking of certain values in packets that are destined for UDP port 18999 of an affected device. An attacker could exploit this vulnerability by sending malicious packets to an affected device. When the packets are processed, an exploitable buffer overflow condition may occur. A successful exploit could allow the attacker to execute arbitrary code on the affected device with elevated privileges. The attacker could also leverage this vulnerability to cause the device to reload, causing a temporary DoS condition while the device is reloading. The malicious packets must be destined to and processed by an affected device. Traffic transiting a device will not trigger the vulnerability. Cisco Bug IDs: CSCvf73881.

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 buffer overflow vulnerability exists in the QoS subsystem of Cisco IOS and IOS XE software due to improper bounds checking of values in packets destined for UDP port 18999. An unauthenticated remote attacker can send malicious packets to trigger the overflow, potentially executing arbitrary code with elevated privileges or causing the device to reload.

MitigationApply the relevant Cisco software update (patch) from Cisco for affected IOS/IOS XE versions. Until patched, filter or block untrusted traffic destined to UDP port 18999 at network perimeter devices.

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
Ios XeOperating system
Affected:= 16.5.1all versions

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
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 OS
    Use 'show version' or 'show inventory' to confirm the device runs Cisco IOS XE software
    Affected if The device does not run Cisco IOS XE (this CVE affects only IOS XE, not classic IOS)
  2. Check the IOS XE version
    Execute 'show version' and locate the firmware version string (for example, Version 16.5.1)
    Affected if The installed version is 16.5.1 or falls within the affected version range for this CVE
  3. Determine if UDP port 18999 is accessible
    Use 'show udp' or 'show ip socket' to list active UDP listeners; alternatively, scan the device from an external host using nmap -sU -p 18999
    Affected if UDP port 18999 is open and listening on the device
  4. Verify if QoS features are enabled
    Run 'show QoS' or 'show policy-map' to check for active quality of service configurations
    Affected if QoS is enabled and policy maps are active on any interface
  5. Review access control at network boundaries
    Inspect edge firewall or ACL configurations to determine if UDP port 18999 traffic from untrusted sources is permitted
    Affected if UDP port 18999 traffic from external/untrusted networks is allowed without restriction

A device is affected if it runs Cisco IOS XE version 16.5.1, has UDP port 18999 open, and has QoS enabled, with the port accessible from untrusted network segments.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the relevant Cisco software update (patch) from Cisco for affected IOS/IOS XE versions. Until patched, filter or block untrusted traffic destined to UDP port 18999 at network perimeter devices.

Recommended fix Moderate confidence

Obtain fixed IOS XE release from Cisco (refer to Cisco Security Advisory for CSCvf73881)

  1. Contact Cisco directly or visit the Cisco Security Advisories page to obtain the specific fixed release for CSCvf73881
  2. Identify the current IOS XE version running on affected devices using 'show version' command
  3. Plan maintenance window for upgrade procedure
  4. Download the fixed IOS XE release from Cisco (typically available on cisco.com with valid service contract)
  5. Follow standard Cisco IOS XE upgrade procedure: upload new image via FTP/TFTPSCP to device, set boot variable, reload device
  6. Verify the device reloads successfully and is running the fixed version with 'show version'
  7. Confirm the QoS subsystem is functioning normally after upgrade
Caveat Check Cisco release notes for any feature changes or migration considerations between versions

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Ios Xe Exploited in the wild — priority engagement
  • Consultation6.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,730
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Scan for this in your stack

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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-2018-0151 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