Exploited CVEs / Cisco / CVE-2017-12240
CVE-2017-12240
Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2022-03-24 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Cisco Security Advisories (PSIRT), linked below.
Actively exploited Cisco IOS and IOS XE Software vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2022-03-03.
Risk summary
Updated July 27, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2017-12240
This flaw lives in the DHCP relay subsystem of Cisco IOS and IOS XE, so any router or switch acting as a DHCP relay agent can be taken over by an unauthenticated attacker sending crafted DHCP packets. It carries a Critical severity rating (CVSS 9.8) and is on the CISA KEV list with confirmed exploitation since March 2022, meaning these are foundational network devices where full compromise gives an attacker control of your traffic path.
Do this: Identify every IOS and IOS XE device configured with ip helper-address or DHCP relay and apply Cisco's fixed software release, or disable relay where it is not needed.
AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2017-12240
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2017-12240
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
CISA required action
Federal (BOD 22-01) remediation due date: 2022-03-24 (past due).
Apply updates per vendor instructions.
Official fix for CVE-2017-12240
The authoritative fix and affected-version list are published by the vendor. Find the IOS and IOS XE Software advisory on Cisco Security Advisories (PSIRT).
Common questions about CVE-2017-12240
Is CVE-2017-12240 actively exploited?
Yes. CVE-2017-12240 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2022-03-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 14%.
What is the CISA deadline and required action for CVE-2017-12240?
CISA set the federal (BOD 22-01) remediation due date at 2022-03-24, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.
What fixes CVE-2017-12240?
The authoritative fix is in the vendor advisory: see Cisco Security Advisories (PSIRT) for the patched IOS and IOS XE Software versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2017-12240?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2017-12240's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
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