CVE-2018-0173A 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…
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CISA lists it as known exploited since Mar 3, 2022; federal agencies had to remediate by Mar 17, 2022. Treat that date as your deadline.
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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.
- CVSS
- 8.6 HIGH (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
- Weakness (CWE)
- CWE-20
- Known exploited
- Added to CISA KEV Mar 3, 2022; federal remediation due Mar 17, 2022Apply updates per vendor instructions.
- EPSS (exploitation in the next 30 days)
- 7.61% (percentile 94)
- Assigned by
- cisco
- NVD analysis
- Analyzed
- Record last updated
- Jan 12, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
cisco ios cisco:ios | denali-16.3.4; through 15.2\(6\)e0a; through 15.2\(4a\)ea5 | NVD |
cisco ios_xe cisco:ios_xe | denali-16.3.4; through 15.2\(6\)e0a; through 15.2\(4a\)ea5 | NVD |
References
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-dhcpr2x-refsource-confirm, vendor-advisory
- http://www.securityfocus.com/bid/103545vdb-entry, x-refsource-bid, broken-link, third-party-advisory
- https://ics-cert.us-cert.gov/advisories/ICSA-18-107-04x-refsource-misc, third-party-advisory, us-government-resource
- https://www.tenable.com/security/research/tra-2018-06x-refsource-misc, third-party-advisory
- http://www.securitytracker.com/id/1040591vdb-entry, x-refsource-sectrack, broken-link, third-party-advisory
- https://ics-cert.us-cert.gov/advisories/ICSA-18-107-05x-refsource-misc, third-party-advisory, us-government-resource
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-0173us-government-resource
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.