CVE-2018-0173

Exp

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.

Published: 2018-03-28 Last update: 2026-01-14 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-0173 is rated Critical Active Threat (92.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 5.42%). CISA KEV confirms active exploitation (added 2022-03-03) affecting Cisco / IOS and IOS XE Software. a weakness (CWE-20) Unauthenticated remote administrative access may be possible. EPSS rose +1.36% over the last day, indicating growing attacker interest. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2018-0173

Name: Cisco IOS and IOS XE Software Improper Input Validation Vulnerability · CISA KEV detail

Exploit added: 2022-03-03

Action due: 2022-03-17

Required action: Apply updates per vendor instructions.

Exploit prediction scoring system (EPSS) score for CVE-2018-0173

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-07 4.07% 5.42% +1.36%
2 2025-12-18 5.61% 4.07% -1.54%
3 2025-12-16 — 5.61% —

Full EPSS history (17 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-0173

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 4.0 [email protected]
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 4.0 134c704f-9b21-4f2e-91b3-4a467353bcc0
7.8 2.0 HIGH
AV:N/AC:L/Au:N/C:N/I:N/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 6.9 [email protected]

Weakness enumeration for CVE-2018-0173

Affected software / configurations for CVE-2018-0173

Vendor Product Version Raw CPE
cisco ios denali-16.3.4 cpe:2.3:o:cisco:ios:denali-16.3.4:*:*:*:*:*:*:*
cisco ios_xe denali-16.3.4 cpe:2.3:o:cisco:ios_xe:denali-16.3.4:*:*:*:*:*:*:*
cisco ios <= 15.2\(6\)e0a cpe:2.3:o:cisco:ios:*:*:*:*:*:*:*:*
cisco ios_xe <= 15.2\(6\)e0a cpe:2.3:o:cisco:ios_xe:*:*:*:*:*:*:*:*
cisco ios <= 15.2\(4a\)ea5 cpe:2.3:o:cisco:ios:*:*:*:*:*:*:*:*
cisco ios_xe <= 15.2\(4a\)ea5 cpe:2.3:o:cisco:ios_xe:*:*:*:*:*:*:*:*

References for CVE-2018-0173

cvelogic Threat Intelligence