Security readout for executives and security teams
Plain-English summary
This is a critical Cisco network-device vulnerability. A remote, unauthenticated attacker could send a crafted DHCPv4 packet to affected IOS or IOS XE systems and potentially take full control or force a reload. CISA lists it as known exploited, so exposed infrastructure should be treated as urgent.
Executive priority
Make this a near-term infrastructure remediation item. The issue affects core network control points, requires no authentication, carries full compromise and outage impact, and is listed by CISA as known exploited.
Technical view
CVE-2017-12240 is a DHCP relay subsystem buffer overflow in Cisco IOS 12.2 through 15.6 and IOS XE. The CVSS 3.1 score is 9.8, with network attack vector, low complexity, no privileges, and high confidentiality, integrity, and availability impact. The CVE maps to CWE-20.
Likely exposure
Organizations running Cisco IOS or IOS XE devices with DHCP relay functionality are the likely exposure group. The bundle does not identify exact device models, fixed releases, or configuration-specific prerequisites beyond DHCP relay and crafted DHCPv4 packet handling.
Exploitation context
CISA KEV inclusion supports known exploitation. The provided bundle does not include exploit timing, observed campaigns, public exploit details, or indicators of compromise. Treat internet- or untrusted-network-reachable DHCP relay paths as higher priority.
Researcher notes
The source bundle confirms affected software families, CVSS, CWE, impact, crafted DHCPv4 trigger, Cisco bug IDs, and KEV status. It does not provide fixed-version tables, model lists, exploit samples, or detection indicators, so validation should rely on Cisco guidance and local configuration review.
Mitigation direction
- Consult Cisco advisory cisco-sa-20170927-dhcp for fixed software and upgrade guidance.
- Prioritize remediation for IOS and IOS XE devices handling DHCP relay traffic.
- Restrict DHCP-related traffic to trusted network segments where operationally possible.
- Review Cisco Bug IDs CSCsm45390 and CSCuw77959 for vendor-specific status.
- Track CISA KEV deadlines and internal remediation exceptions.
Validation and detection
- Inventory Cisco IOS and IOS XE versions across routers and switches.
- Identify devices using DHCP relay or forwarding DHCPv4 traffic.
- Compare software versions against Cisco advisory guidance.
- Confirm remediated devices are no longer on vulnerable release trains.
- Review device reload history and security monitoring for unexplained DHCP-related instability.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2017-12240 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959CVE reference · x_refsource_CONFIRM
- https://quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390CVE reference · x_refsource_CONFIRM
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-dhcpCVE reference · x_refsource_CONFIRM
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-12240CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.