Threats / Cisco / CVE-2017-12240
CVE-2017-12240
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Cisco IOS and XE Software vulnerability
A DHCP relay subsystem vulnerability in Cisco IOS and IOS XE Software allows unauthenticated remote attackers to execute arbitrary code and gain full control of affected devices.
Verdict
Today item — known-exploited.
An unauthenticated remote attacker can exploit improper input validation in the DHCP relay subsystem to achieve arbitrary code execution and complete system compromise on vulnerable Cisco network infrastructure.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
2 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-03-03).
Probability (EPSS)
EPSS 0.13521 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Cisco, IOS and IOS XE Software. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-20 Improper Input Validation.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious DHCP packet and send it to the relay subsystem without authentication.
Business
Network infrastructure becomes a direct attack vector requiring no credentials or prior access.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the input validation flaw to inject and execute arbitrary code on the device.
Business
Attackers gain full administrative control over critical routing and switching infrastructure.
3
Lateral reach — past segmentation narrative 3
Attacker
I maintain persistence and pivot through the compromised device to other network segments.
Business
Enterprise network segmentation fails; lateral movement enables compromise of downstream systems and data exfiltration.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05