CVE-2017-12240The 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…
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CISA lists it as known exploited since Mar 3, 2022; federal agencies had to remediate by Mar 24, 2022. Treat that date as your deadline.
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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.
- CVSS
- 9.8 CRITICAL (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-20
- Known exploited
- Added to CISA KEV Mar 3, 2022; federal remediation due Mar 24, 2022Apply updates per vendor instructions.
- EPSS (exploitation in the next 30 days)
- 13.77% (percentile 96)
- Assigned by
- cisco
- NVD analysis
- Analyzed
- Record last updated
- Jan 12, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
cisco ios cisco:ios | from 12.2 through 15.6 | NVD |
References
- https://quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959x-refsource-confirm, vendor-advisory
- https://quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390x-refsource-confirm, vendor-advisory
- http://www.securityfocus.com/bid/101034vdb-entry, x-refsource-bid, broken-link, third-party-advisory
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-dhcpx-refsource-confirm, vendor-advisory
- http://www.securitytracker.com/id/1039445vdb-entry, x-refsource-sectrack, broken-link, third-party-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2017-12240us-government-resource
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.