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iOSOperating system · Cisco

CVE-2018-15373

HIGH · 7.4 CVSS v3.0 Published 2018-10-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
79/100
Remediation priority · High
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 implementation of Cisco Discovery Protocol functionality in Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to exhaust memory on an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to improper memory handling by the affected software when the software processes high rates of Cisco Discovery Protocol packets that are sent to a device. An attacker could exploit this vulnerability by sending a high rate of Cisco Discovery Protocol packets to an affected device. A successful exploit could allow the attacker to exhaust memory on the affected device, resulting in a DoS condition.

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 memory exhaustion vulnerability in Cisco IOS and IOS XE Software allows an unauthenticated, adjacent attacker to send high rates of Cisco Discovery Protocol (CDP) packets to an affected device, exhausting memory and causing denial of service. The vulnerability stems from improper memory handling when processing CDP packets.

MitigationDisable Cisco Discovery Protocol on interfaces where it is not required, or implement network segmentation and access control lists (ACLs) to restrict CDP packet sources to trusted devices. Apply the relevant Cisco software patch from the vendor advisory.

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
iOSOperating system
Affected:= 15.5\(3\)s3.16
Ios XeOperating system
Affected:= 15.5\(3\)s3.16

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.0/AV:A/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify the device OS and version
    Run 'show version' or 'show version | include IOS' to determine if the device runs Cisco IOS or IOS XE and note the exact software version number
    Affected if The device runs Cisco IOS or IOS XE and the version falls within or below 15.5(3)S3 (or the specific version range provided in the advisory)
  2. Verify CDP is enabled on any interfaces
    Run 'show cdp neighbor' or 'show cdp interface' to list interfaces where Cisco Discovery Protocol is active
    Affected if CDP is enabled on one or more interfaces - the vulnerability only affects devices actively processing CDP packets
  3. Check for abnormally high memory utilization
    Run 'show memory summary' or 'show processes memory' to review current memory usage statistics and look for unusually high utilization or memory allocation failures
    Affected if Memory usage is excessively high or showing allocation errors consistent with the exhaustion condition described in the CVE
  4. Review CDP packet processing statistics
    Run 'show interface' or specific CDP-related show commands to examine CDP packet counters and verify if unusually high inbound CDP traffic volumes are being received
    Affected if CDP packet counters show abnormally high inbound traffic rates, indicating potential exploitation attempts

A device is affected if it runs a vulnerable Cisco IOS or IOS XE version within the stated range AND has CDP enabled on at least one interface, making it susceptible to the memory exhaustion attack from adjacent CDP packets.

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

Disable Cisco Discovery Protocol on interfaces where it is not required, or implement network segmentation and access control lists (ACLs) to restrict CDP packet sources to trusted devices. Apply the relevant Cisco software patch from the vendor advisory.

Fix this in iOS Scoped from the published advisory
  • Consultation8.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,380
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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-2018-15373 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