CVE-2017-12240

Name: CVE-2017-12240
Creator: NVD / NIST
Published: 2017-09-29T01:34:49.077+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10Actively ExploitedEPSS 13.52%

Last modified Jun 17, 2026

CVE-2017-12240 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. CISA has confirmed active exploitation in the wild. EPSS estimates a 13.52% chance of exploitation in the next 30 days.

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

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

13.52%

96.0th percentile

Probability of exploitation in the next 30 days. Learn more

Exploitation Status

This vulnerability is listed in CISA’s Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. Federal agencies must remediate by Mar 24, 2022.

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Cisco	Ios	>= 12.2, <= 15.6

References

http://www.securityfocus.com/bid/101034Broken Link, Third Party Advisory, VDB Entry
http://www.securitytracker.com/id/1039445Broken Link, Third Party Advisory, VDB Entry
https://quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390Vendor Advisory
https://quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959Vendor Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-dhcpVendor Advisory
http://www.securityfocus.com/bid/101034Broken Link, Third Party Advisory, VDB Entry
http://www.securitytracker.com/id/1039445Broken Link, Third Party Advisory, VDB Entry
https://quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390Vendor Advisory
https://quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959Vendor Advisory
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-dhcpVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-12240US Government Resource

Timeline

Published: Sep 29, 2017
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2017-12240?

How severe is CVE-2017-12240?

CVE-2017-12240 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 13.52% probability of exploitation in the next 30 days. This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog.

How do I fix CVE-2017-12240?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2017-12240?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST