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Vulnerabilities

Vulnerability · CVE-2017-12240

Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability

Published Sep 28, 2017 · catalog updated Jun 16, 2026 · Cisco IOS and IOS XE Software

Patch now

CVE-2017-12240 is in the CISA known-exploited catalog, due Mar 24, 2022. Confirm Cisco IOS and IOS XE Software against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
Critical9.8
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
13.77%
Remediation
Remediation guidance
Affected products
cpe cisco/ios · vendor Cisco IOS and IOS XE Software

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe cisco/iosversion unspecified
  • vendor Cisco IOS and IOS XE Softwareversion unspecified

How to fix CVE-2017-12240

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2017-12240 is in the CISA known-exploited catalog, due Mar 24, 2022. Confirm Cisco IOS and IOS XE Software against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply updates per vendor instructions.

What should an analyst verify?

CWE-119: Buffer Overflow; CWE-20: Improper Input Validation. EPSS 13.77%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Sep 28, 2017 · Catalog

    Detected

    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

  2. Mar 3, 2022 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. Mar 24, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. Jun 16, 2026 · Catalog

    Updated

    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

Sources

  • CISA KEVConfirmed exploitationCVE-2017-12240

    The Dynamic Host Configuration Protocol (DHCP) relay subsystem of Cisco IOS 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.

    cisa.gov
  • CVE.orgVulnerability recordCVE-2017-12240

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2017-12240

    30-day exploitation probability 13.8%

    first.org
  • NIST NVDVulnerability recordCVE-2017-12240

    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

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2017-12240

    The Dynamic Host Configuration Protocol (DHCP) relay subsystem of Cisco IOS 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.

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 17, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.