CVE-2017-12240
Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability is confirmed as actively exploited and is listed in the CISA KEV catalog.
Required action
Apply updates per vendor instructions.
CISA notes
https://nvd.nist.gov/vuln/detail/CVE-2017-12240
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.
Severity
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation Context
as of October 14, 2026- CISA added CVE-2017-12240 to the KEV catalog 1,617 days after its CVE record was published.
- It is one of 100 Cisco entries in the CISA KEV catalog, and one of 50 added in 2022.
- Its current EPSS score (13.8%) is higher than that of 29% of CISA KEV entries.
Affected Products
| Vendor | Product | Affected versions |
|---|---|---|
| - | Cisco IOS and IOS XE | Cisco IOS and IOS XE |
References
5 LinksRecord Details
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Tool categories
CVE record data © The MITRE Corporation, used under the CVE Terms of Use. Exploited-in-the-wild data from the CISA Known Exploited Vulnerabilities catalog (CC0). Exploit prediction scores by FIRST EPSS (first.org/epss). This site is not endorsed or certified by MITRE, NVD, CISA, or FIRST.