CVE-2017-12240

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2022-03-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 4 sources updated this weekExploited in the wild
9.8EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV)
CISA-KEV: ExploitedEPSS PROB: 14%CVSS: 9.8Exploit: cisa kev · ssvc active · epss top5pctExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
9.8
EG Score
9.8(high)
EG Risk
99(Act)
EG Risk 99/100SSVC: Act

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
14%
EPSS %ILE
96%
KEV
⚠ Exploited

Published

September 29, 2017

Last Modified

June 17, 2026

Advisory Details (5)

Auto-updated Sep 8, 2026
⚠️ Active exploitation confirmed. No patch confirmed yet.
generic🔴 Active Exploitation

Cisco IOS and IOS XE Software DHCP Remote Code Execution Vulnerability

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927-dhcp
generic

Bug Search Tool

https://quickview.cloudapps.cisco.com/quickview/bug/CSCuw77959
generic

Bug Search Tool

https://quickview.cloudapps.cisco.com/quickview/bug/CSCsm45390
generic🔴 Active Exploitation

CVE-2017-12240 - PSIRT.COM

http://www.securityfocus.com/bid/101034
generic
http://www.securitytracker.com/id/1039445

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 56× in last 7d / 240× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 805 total refreshes for this CVE.

  1. 2026-09-08 09:55 UTCGHSA enrichment
  2. 2026-09-08 05:54 UTCGHSA enrichment
  3. 2026-09-08 01:52 UTCGHSA enrichment
  4. 2026-09-07 21:50 UTCGHSA enrichment
  5. 2026-09-07 17:49 UTCEG score recompute
  6. 2026-09-07 17:49 UTCGHSA enrichment
  7. 2026-09-07 15:56 UTCEPSS rescore
  8. 2026-09-07 13:47 UTCGHSA enrichment
  9. 2026-09-07 09:42 UTCGHSA enrichment
  10. 2026-09-07 05:38 UTCGHSA enrichment
  11. 2026-09-07 01:36 UTCGHSA enrichment
  12. 2026-09-06 21:31 UTCGHSA enrichment
  13. 2026-09-06 17:30 UTCEG score recompute
  14. 2026-09-06 17:30 UTCGHSA enrichment
  15. 2026-09-06 13:29 UTCGHSA enrichment
  16. 2026-09-06 09:28 UTCGHSA enrichment
  17. 2026-09-06 05:27 UTCGHSA enrichment
  18. 2026-09-06 01:26 UTCGHSA enrichment
  19. 2026-09-05 21:24 UTCGHSA enrichment
  20. 2026-09-05 17:23 UTCEG score recompute
  21. 2026-09-05 17:23 UTCGHSA enrichment
  22. 2026-09-05 13:19 UTCGHSA enrichment
  23. 2026-09-05 09:19 UTCGHSA enrichment
  24. 2026-09-05 05:17 UTCGHSA enrichment
  25. 2026-09-05 01:13 UTCGHSA enrichment
Show 75 more
  1. 2026-09-04 21:12 UTCGHSA enrichment
  2. 2026-09-04 17:38 UTCCISA KEV update
  3. 2026-09-04 17:11 UTCEG score recompute
  4. 2026-09-04 17:11 UTCGHSA enrichment
  5. 2026-09-04 13:56 UTCEPSS rescore
  6. 2026-09-04 13:09 UTCGHSA enrichment
  7. 2026-09-04 09:08 UTCGHSA enrichment
  8. 2026-09-04 05:07 UTCEG score recompute
  9. 2026-09-04 05:07 UTCGHSA enrichment
  10. 2026-09-04 05:01 UTCEPSS rescore
  11. 2026-09-04 01:05 UTCGHSA enrichment
  12. 2026-09-03 21:02 UTCGHSA enrichment
  13. 2026-09-03 17:01 UTCGHSA enrichment
  14. 2026-09-03 12:58 UTCGHSA enrichment
  15. 2026-09-03 08:52 UTCGHSA enrichment
  16. 2026-09-03 04:46 UTCGHSA enrichment
  17. 2026-09-03 00:43 UTCGHSA enrichment
  18. 2026-09-02 20:43 UTCGHSA enrichment
  19. 2026-09-02 17:33 UTCCISA KEV update
  20. 2026-09-02 16:42 UTCEG score recompute
  21. 2026-09-02 16:42 UTCGHSA enrichment
  22. 2026-09-02 14:07 UTCEPSS rescore
  23. 2026-09-02 12:38 UTCGHSA enrichment
  24. 2026-09-02 08:34 UTCGHSA enrichment
  25. 2026-09-02 04:30 UTCGHSA enrichment
  26. 2026-09-02 00:24 UTCGHSA enrichment
  27. 2026-09-01 20:20 UTCGHSA enrichment
  28. 2026-09-01 16:19 UTCEG score recompute
  29. 2026-09-01 16:19 UTCGHSA enrichment
  30. 2026-09-01 13:48 UTCEPSS rescore
  31. 2026-09-01 12:18 UTCGHSA enrichment
  32. 2026-09-01 08:17 UTCGHSA enrichment
  33. 2026-09-01 04:17 UTCEG score recompute
  34. 2026-09-01 04:17 UTCGHSA enrichment
  35. 2026-09-01 03:31 UTCEPSS rescore
  36. 2026-09-01 00:15 UTCGHSA enrichment
  37. 2026-08-31 20:11 UTCGHSA enrichment
  38. 2026-08-31 16:06 UTCGHSA enrichment
  39. 2026-08-31 14:19 UTCCISA KEV update
  40. 2026-08-31 12:05 UTCGHSA enrichment
  41. 2026-08-31 08:02 UTCGHSA enrichment
  42. 2026-08-31 04:01 UTCGHSA enrichment
  43. 2026-08-31 00:00 UTCGHSA enrichment
  44. 2026-08-30 20:00 UTCEG score recompute
  45. 2026-08-30 20:00 UTCGHSA enrichment
  46. 2026-08-30 19:13 UTCEPSS rescore
  47. 2026-08-30 15:59 UTCGHSA enrichment
  48. 2026-08-30 11:58 UTCGHSA enrichment
  49. 2026-08-30 07:57 UTCGHSA enrichment
  50. 2026-08-30 03:56 UTCEG score recompute
  51. 2026-08-30 03:56 UTCGHSA enrichment
  52. 2026-08-29 23:55 UTCGHSA enrichment
  53. 2026-08-29 19:54 UTCGHSA enrichment
  54. 2026-08-29 15:53 UTCGHSA enrichment
  55. 2026-08-29 11:51 UTCGHSA enrichment
  56. 2026-08-29 07:49 UTCGHSA enrichment
  57. 2026-08-29 03:48 UTCGHSA enrichment
  58. 2026-08-28 23:46 UTCEG score recompute
  59. 2026-08-28 23:46 UTCGHSA enrichment
  60. 2026-08-28 21:36 UTCEPSS rescore
  61. 2026-08-28 19:44 UTCGHSA enrichment
  62. 2026-08-28 15:37 UTCGHSA enrichment
  63. 2026-08-28 11:27 UTCGHSA enrichment
  64. 2026-08-28 07:21 UTCGHSA enrichment
  65. 2026-08-28 03:19 UTCGHSA enrichment
  66. 2026-08-27 23:15 UTCGHSA enrichment
  67. 2026-08-27 19:14 UTCGHSA enrichment
  68. 2026-08-27 17:22 UTCCISA KEV update
  69. 2026-08-27 15:13 UTCEG score recompute
  70. 2026-08-27 15:13 UTCGHSA enrichment
  71. 2026-08-27 14:20 UTCEPSS rescore
  72. 2026-08-27 11:12 UTCGHSA enrichment
  73. 2026-08-27 07:10 UTCGHSA enrichment
  74. 2026-08-27 03:09 UTCGHSA enrichment
  75. 2026-08-26 23:09 UTCGHSA enrichment

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Frequently asked(6)

What is CVE-2017-12240?
CVE-2017-12240 is a critical vulnerability published on September 29, 2017. 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,…
When was CVE-2017-12240 disclosed?
CVE-2017-12240 was first published in the National Vulnerability Database on September 29, 2017, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2017-12240 actively exploited?
Yes. CISA added CVE-2017-12240 to the Known Exploited Vulnerabilities catalog on March 3, 2022, affecting Cisco IOS and IOS XE Software. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2017-12240?
CVE-2017-12240 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2017-12240?
CVE-2017-12240 affects Cisco IOS and IOS XE Software. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2017-12240?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2017-12240, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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