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CVE-2017-12240

Critical 9.8 Exploited in the wild (KEV)

Confirmed active exploitation — CISA KEV catalog

Name
Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability
Added to catalog
Remediation due date (US federal)
Required action
Apply updates per vendor instructions.

Description

The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code and gain full control of an affected system. The attacker could also cause an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to a buffer overflow condition in the DHCP relay subsystem of the affected software. An attacker could exploit this vulnerability by sending a crafted DHCP Version 4 (DHCPv4) packet to an affected system. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a DoS condition. Cisco Bug IDs: CSCsm45390, CSCuw77959.

Metrics

CVSS 3.1
9.8 (CRITICAL) Score source: NVD CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS — exploit probability
14% (percentile: 97) as of 1 November 2026
CWE
CWE-20, CWE-119

Affected products

cisco: ios; cisco: 1000 integrated services router; cisco: 1100-4g integrated services router; cisco: 1100-4gltegb integrated services router; cisco: 1100-4gltena integrated services router; cisco: 1100-4p integrated services router; cisco: 1100-6g integrated services router; cisco: 1100-8p integrated services router; cisco: 1100-lte integrated services router; cisco: 1100 integrated services router; cisco: 1101-4p integrated services router; cisco: 1101 integrated services router; cisco: 1109-2p integrated services router; cisco: 1109-4p integrated services router; cisco: 1109 integrated services router

References