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

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: yes — in CISA KEV since 2022-03-03
EPSS: 7.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2018-03-28 · updated 2026-06-17
Weakness: 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.

Affected products

Cisco IOS: through 15.2\(6\)e0a; through 15.2\(4a\)ea5; denali-16.3.4
Cisco IOS XE: through 15.2\(6\)e0a; through 15.2\(4a\)ea5; denali-16.3.4

References

Get alerted when CVE-2018-0173 or the next vulnerability affects your stack