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Vulnerabilities

Vulnerability · CVE-2018-0173

Cisco IOS and IOS XE Software Improper Input Validation Vulnerability

Published Mar 28, 2018 · catalog updated Jun 16, 2026 · Cisco IOS and IOS XE Software

Patch now

CVE-2018-0173 is in the CISA known-exploited catalog, due Mar 17, 2022. Confirm Cisco IOS and IOS XE Software against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
High8.6
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
7.61%
Remediation
Remediation guidance
Affected products
cpe cisco/ios · cpe cisco/ios xe · vendor Cisco IOS and IOS XE Software

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe cisco/iosdenali-16.3.4
  • cpe cisco/ios xedenali-16.3.4
  • vendor Cisco IOS and IOS XE Softwareversion unspecified

How to fix CVE-2018-0173

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2018-0173 is in the CISA known-exploited catalog, due Mar 17, 2022. Confirm Cisco IOS and IOS XE Software against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with cisco/ios xe denali-16.3.4. Apply updates per vendor instructions.

What should an analyst verify?

CWE-20: Improper Input Validation. EPSS 7.61%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 28, 2018 · Catalog

    Detected

    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 validatio

  2. Mar 3, 2022 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. Mar 17, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    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 validatio

Sources

  • CISA KEVConfirmed exploitationCVE-2018-0173

    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 can allow for denial-of-service (DoS).

    cisa.gov
  • CVE.orgVulnerability recordCVE-2018-0173

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2018-0173

    30-day exploitation probability 7.6%

    first.org
  • NIST NVDVulnerability recordCVE-2018-0173

    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 denia

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2018-0173

    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 can allow for denial-of-service (DoS).

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.