# CVE-2018-0173: Cisco IOS and IOS XE Software Improper Input Validation Vulnerability

> CVE-2018-0173: Cisco IOS and IOS XE Software Improper Input Validation Vulnerability. CVSS 8.6 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2018-0173
Last updated: 2026-01-12T22:00:15Z

- Published: 2018-03-28 22:00 UTC · Updated: 2026-01-12 22:00 UTC · Assigner: cisco
- CVSS: 8.6 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- EPSS: 7.6%, 95th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2022-03-03, federal due date 2022-03-17, ransomware use: Unknown
- CWE: CWE-20

## Description

A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a Relay Reply denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of encapsulated option 82 information that it receives in DHCPOFFER messages from DHCPv4 servers. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device, which the device would then forward to a DHCPv4 server. When the affected software processes the option 82 information that is encapsulated in the response from the server, an error could occur. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvg62754.

## CISA required action

Apply updates per vendor instructions.

## Affected vendors and products

- n/a: Cisco IOS and IOS XE

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2018-0173)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2018-0173)
- [https://ics-cert.us-cert.gov/advisories/ICSA-18-107-04](https://ics-cert.us-cert.gov/advisories/ICSA-18-107-04)
- [https://ics-cert.us-cert.gov/advisories/ICSA-18-107-05](https://ics-cert.us-cert.gov/advisories/ICSA-18-107-05)
- [https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr2](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr2)
- [https://www.tenable.com/security/research/tra-2018-06](https://www.tenable.com/security/research/tra-2018-06)
- [http://www.securityfocus.com/bid/103545](http://www.securityfocus.com/bid/103545)
- [http://www.securitytracker.com/id/1040591](http://www.securitytracker.com/id/1040591)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2018-0173 · Markdown: https://rewindex.com/cve/CVE-2018-0173.md · JSON: https://rewindex.com/api/v1/cves/CVE-2018-0173 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:13:19.112Z