9.8 Critical Exploited

CVE-2017-12240 Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability

Active exploitation observed

· CISA KEV catalogue

Required action Apply updates per vendor instructions.

Ransomware campaigns Not observed so far

Weakness CWE-20

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.

Affected products and versions

Product	Affected versions	Fixed in
Cisco IOS and IOS XE	Versions not published

References

quickview.cloudapps.cisco.com quickview.cloudapps.cisco.com
quickview.cloudapps.cisco.com quickview.cloudapps.cisco.com
101034 www.securityfocus.com
tools.cisco.com tools.cisco.com
1039445 www.securitytracker.com

Timeline

Published September 28, 2017
Added to the KEV catalogue March 3, 2022
Last modified January 12, 2026

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