---
id: "CVE-2018-0174"
kind: "vulnerability"
aliases: ["CVE-2018-0174"]
title: "Cisco IOS XE Software: Cisco IOS Software and Cisco IOS XE Software Improper Input Validation Vulnerability"
severity: "high"
cvss: 8.6
epss: 0.07608
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Cisco IOS XE Software", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["cisco", "dhcp", "exploited", "infrastructure", "ios-xe", "network-gear"]
not_affected_if: ["dhcp-option-82-unused", "non-cisco-hardware"]
published_at: "2018-03-28T22:29:01+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2018-0174", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2018-0174", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2018-0174", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Cisco IOS XE Software: Cisco IOS Software and Cisco IOS XE Software Improper Input Validation Vulnerability

A flaw in the DHCP option 82 handling of Cisco IOS and IOS XE lets a crafted packet crash or hang the device. An attacker gets a denial of service on the router or switch, not code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Cisco IOS XE Software affected ? fixed ?

## Fix

Apply the Cisco IOS or IOS XE update named in the vendor advisory for CVE-2018-0174.
CISA KEV lists it as known exploited; apply updates per vendor instructions.

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2018-0174
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2018-0174
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2018-0174

## From the sources

A vulnerability in the DHCP option 82 encapsulation functionality of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of option 82 information that it receives in DHCP Version 4 (DHCPv4) packets from DHCP relay agents. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCuh91645.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_