What is CVE-2017-12240?

CVE-2017-12240 is a critical-severity vulnerability in Cisco 1000 Integrated Services Router, classified under Improper Input Validation. CVSS score: 9.8/10. Published 2017-09-29.

How severe is CVE-2017-12240?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2017-12240 known to be exploited?

Yes. CVE-2017-12240 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-03), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.

Buffer overflow in Cisco 1000 Integrated Services Router

CVE-2017-12240

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2017-09-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.138 (96.5th percentile), scored 2026-10-19.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 96th percentile — 96.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.138 · newest: 0.138 · change: 0.000

Affected products

Weakness classification (CWE)

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2022-03-03. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2022-03-24.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959 (Vendor Advisory)
quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390 (Vendor Advisory)
www.securityfocus.com/bid/101034 (VDB Entry, Third Party Advisory, vdb-entry, Broken Link)
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927… (Vendor Advisory)
www.securitytracker.com/id/1039445 (VDB Entry, Third Party Advisory, vdb-entry, Broken Link)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2017-12240?: CVE-2017-12240 is a critical-severity vulnerability in Cisco 1000 Integrated Services Router, classified under Improper Input Validation. CVSS score: 9.8/10. Published 2017-09-29.
How severe is CVE-2017-12240?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2017-12240 known to be exploited?: Yes. CVE-2017-12240 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-03), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.