CVE-2018-0173
HighExploitedPublic exploitA 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…
Published Mar 28, 2018 · Updated Jan 14, 2026
Key Facts
Patch immediately- CVE-2018-0173 is a high-severity vulnerability (CVSS 8.6 v3.1) affecting IOS (Cisco), IOS Xe (Cisco), Cisco IOS and IOS XE.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 3, 2022. Public exploit code is available.
- EPSS estimates a 7.6% probability of exploitation in the next 30 days.
- Fixed versions are available, including IOS <=15.2\(6\)e0a, IOS Xe <=15.2\(6\)e0a, IOS 15.2\(6\)e0a.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
8.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
EPSS (30-day exploit likelihood)
7.6%
Higher than 94.4% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2018-0173 brief as a PDF
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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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Mar 3, 2022 | Mar 17, 2022 | Not reported |
| Industry KEV feed | Mar 3, 2022 | Mar 17, 2022 | Not reported |
| CIRCL KEV | Mar 3, 2022 | Mar 17, 2022 | Not reported |
| ENISA EUVD | Mar 3, 2022 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
5 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| IOSCisco | denali-16.3.4 | 15.2\(6\)e0a |
| IOS XeCisco | denali-16.3.4 | 15.2\(6\)e0a |
| Cisco IOS and IOS XE | >= Cisco IOS and IOS XE | n/a |
Patched Releases
IOS
<=15.2\(6\)e0a
IOS Xe
<=15.2\(6\)e0a
Timeline
Publicly disclosed
Mar 28, 2018
Added to CISA KEV
Mar 3, 2022
Added to Industry KEV feed
Mar 3, 2022
Added to CIRCL KEV
Mar 3, 2022
Added to ENISA EUVD
Mar 3, 2022
Last updated
Jan 14, 2026
Weakness Type
- CWE-20 Improper Input Validation
References
- advisoryhttps://ics-cert.us-cert.gov/advisories/ICSA-18-107-04
- advisoryhttps://ics-cert.us-cert.gov/advisories/ICSA-18-107-05
- advisoryhttps://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr2
- advisoryhttps://www.tenable.com/security/research/tra-2018-06
- advisory103545
FAQ
Common Questions.
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.
Affected: IOS (Cisco) versions denali-16.3.4; IOS Xe (Cisco) versions denali-16.3.4; Cisco IOS and IOS XE versions >= Cisco IOS and IOS XE. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Mar 3, 2022.
Yes. It was added on Mar 3, 2022 with a federal remediation due date of Mar 17, 2022.
Public exploit code is available.
Fixed versions are available, including IOS <=15.2\(6\)e0a, IOS Xe <=15.2\(6\)e0a, IOS 15.2\(6\)e0a.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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