Critical DHCP Remote Code Execution Vulnerability (CVE‑2017‑12240) in Cisco IOS & IOS XE
What It Is — Cisco’s DHCP relay subsystem in IOS and IOS XE contains a flaw that allows an unauthenticated, remote attacker to inject and execute arbitrary code on the device. The vulnerability is tracked as CVE‑2017‑12240 and has a CVSS v3.1 base score of 9.8 (Critical).
Exploitability — Public exploits have been observed; the attack requires only a crafted DHCP packet to a vulnerable router or switch, making it trivially exploitable over the network.
Affected Products — Cisco IOS and Cisco IOS XE software that include the DHCP relay feature (common on edge routers, aggregation switches, and ISP gear).
Why It Matters for Trust & Control Assurance
- Demonstrates the need for continuous vulnerability monitoring of network‑infrastructure assets to keep audit evidence up‑to‑date.
- Highlights gaps in patch‑management and configuration control that can be flagged in a control‑mapping program and reported to auditors.
- Provides a concrete example of why enterprises must maintain a defensible remediation trail for critical infrastructure, a prerequisite for many trust‑focused assessments.
Recommended Actions
- Apply Cisco’s security advisory patch immediately on all affected IOS/IOS XE devices.
- Verify that DHCP relay is disabled where not required, or restrict it to trusted sources.
- Update your asset inventory to tag devices with the DHCP relay subsystem and map the patch status to the “Vulnerability Management” control objective.
- Enable continuous monitoring of firmware versions and configuration drift on network gear.
- Document remediation steps in your audit repository to provide evidence of due diligence.
Source: CISA KEV – CVE‑2017‑12240