Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2018-0171

Cisco IOS and IOS XE Denial of Service

Cisco IOS and IOS XE · Cisco IOS and IOS XE

Watch CVE-2018-0171 Browse KEV feed
Severity
CVSS 9.8 · Critical
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
99.5%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2018-0171 is an unauthenticated vulnerability affecting Cisco IOS and IOS XE. A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV.

Who is affected?

Cisco IOS and IOS XE cisco ios and ios xe.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Cisco IOS and IOS XE Denial of Service

A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition, or to execute arbitrary code on an affected device. The vulnerability is due to improper validation of packet data. An attacker could exploit this vulnerability by sending a crafted Smart Install message to an affected device on TCP port 4786.

A successful exploit could allow the attacker to cause a buffer overflow on the affected device, which could have the following impacts: Triggering a reload of the device, Allowing the attacker to execute arbitrary code on the device, Causing an indefinite loop on the affected device that triggers a watchdog crash. Cisco Bug IDs: CSCvg76186.

n/a Affected
Cisco IOS and IOS XE
Cisco IOS and IOS XE
Published
28 Mar 2018
Exploitation Reported
03 Nov 2021
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

ios cisa windows edge nuclei_scanner

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 03 Nov 2021

A trusted third party reported exploitation.

Proof of concept available

Nuclei Templates

Recorded 12 Jun 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CISA First 2021-11-03 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/javascript/cves/2018/CVE-2018-0171.yaml 01 Jun 2026

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.8 Critical

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

99.5%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Input Validation CWE-20

Recent mention · All CISA Advisories

Improve Router Hygiene to Protect Against Russian State-Sponsored Targeting

Russian Government-Sponsored Activity Targets Poorly Configured and Vulnerable Devices Across Critical Sectors Executive summary Russian Federal Security Service (FSB) Center 16 cyber actors continue to exploit poorly configured and vulnerable networking devices worldwide,...

Read full advisory

All CVSS Scores

CVSS v3.1 9.8 Critical

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v2.0 10.0 High

AV:N/AC:L/Au:N/C:C/I:C/A:C

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Cisco Smart Install - Configuration Download

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 14:21 UTC

    Public PoC available

    Public proof-of-concept code published

  2. 15:34 UTC

    Nuclei template available

    Scanner coverage available

  3. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. 22:00 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2018-0171

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2018-0171",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.99479,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}