CVE-2017-12240

CRITICALNVD 9.89.8
EchelonGraph scoreHIGH confidence

“—” beside the score: it is equal to NVD's CVSS score.

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 Known Exploited Vulnerabilities catalog, EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 3 sources updated this weekExploited in the wild
9.8EG
EchelonGraph verdictMitigate nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV) — the reason this is sooner than the SSVC decision on this page at low mission impact
CISA-KEV: ExploitedEPSS PROB: 14%CVSS: 9.8Exploit: No code on recordExposed services: Not assessed

No fix has been recorded since the CVE record was published in 2017 — use a compensating control (WAF / firewall / segmentation) and check the vendor's advisory.

The CVE record's description, written by its CNA (Cisco Systems, Inc.), states the affected versions: "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 affec…" No release containing a fix is confirmed on record.

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
9.8CRITICALhigh confidence
EG Risk
99
EG Risk 99/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity98% × 45%
Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation100% × 40%
Fixed at 100% for a CISA KEV listing: EchelonGraph's rule.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Attend at low mission impact; Act at medium or high.
Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: No fix has been recorded since the CVE record was published in 2017. Restrict network exposure of the affected system or apply the vendor's mitigation sooner than your standard update timelines at low mission impact and as soon as possible at medium or high, and check the vendor's advisory for a fix.
EPSS PROB
14%
EPSS %ILE
96th
KEV
⚠ Exploited

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.

EG Severity
9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
14% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-23). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
CISA KEV and EG-KEV Tier 1 (exploited in the wild)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Act at medium mission impactAttend at low mission impact; Act at medium or high.CISA BOD 26-04: 3 days & forensic triage if the affected system is publicly exposed; 3 days & forensic triage if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Attend at low mission impact; Act at medium or high.

No fix has been recorded since the CVE record was published in 2017. Restrict network exposure of the affected system or apply the vendor's mitigation sooner than your standard update timelines at low mission impact and as soon as possible at medium or high, and check the vendor's advisory for a fix.

Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)3 days & forensic triage if the affected system is publicly exposed; 3 days & forensic triage if it is not.

In CISA KEV yes (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

CISA required action“Apply updates per vendor instructions.”

Quoted verbatim from CISA's Known Exploited Vulnerabilities catalog. CISA directs it at US federal civilian executive branch agencies under Binding Operational Directive (BOD) 26-04, which replaced BOD 22-01 on 10 June 2026; it is not EchelonGraph's advice. CISA's notes: https://nvd.nist.gov/vuln/detail/CVE-2017-12240

Published

September 29, 2017

Last Modified

June 17, 2026

Advisory Details (5)

Auto-updated Oct 20, 2026
⚠️ Actively exploited (CISA KEV, CISA Vulnrichment). No fix on record since 2017.

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 24× in last 7d / 185× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 1,112 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 1,012 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-23 19:08 UTCEG score recompute
  2. 2026-10-23 19:08 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-10-23 16:26 UTCEPSS rescoreEPSS 14% · 96th percentile
  4. 2026-10-22 20:09 UTCEG score recompute
  5. 2026-10-22 20:08 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  6. 2026-10-22 16:27 UTCEPSS rescoreEPSS 14% · 96th percentile
  7. 2026-10-21 21:09 UTCEG score recompute
  8. 2026-10-21 21:09 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  9. 2026-10-21 16:27 UTCEPSS rescoreEPSS 14% · 96th percentile
  10. 2026-10-20 22:12 UTCEG score recompute
  11. 2026-10-20 22:12 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  12. 2026-10-20 16:27 UTCEPSS rescoreEPSS 14% · 96th percentile
  13. 2026-10-19 23:14 UTCEG score recompute
  14. 2026-10-19 23:13 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  15. 2026-10-19 16:26 UTCEPSS rescoreEPSS 14% · 96th percentile
  16. 2026-10-19 00:15 UTCEG score recompute
  17. 2026-10-19 00:15 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  18. 2026-10-18 16:26 UTCEPSS rescoreEPSS 14% · 96th percentile
  19. 2026-10-18 10:40 UTCEG score recompute
  20. 2026-10-18 01:17 UTCEG score recompute
  21. 2026-10-18 01:17 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  22. 2026-10-17 16:27 UTCEPSS rescoreEPSS 14% · 96th percentile
  23. 2026-10-17 02:20 UTCEG score recompute
  24. 2026-10-17 02:20 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  25. 2026-10-16 16:29 UTCEPSS rescoreEPSS 14% · 96th percentile
Show 75 more
  1. 2026-10-16 03:21 UTCEG score recompute
  2. 2026-10-16 03:21 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  3. 2026-10-15 16:26 UTCEPSS rescoreEPSS 14% · 96th percentile
  4. 2026-10-15 04:23 UTCEG score recompute
  5. 2026-10-15 04:23 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  6. 2026-10-14 16:27 UTCEPSS rescoreEPSS 14% · 96th percentile
  7. 2026-10-14 05:24 UTCEG score recompute
  8. 2026-10-14 05:24 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  9. 2026-10-13 16:27 UTCEPSS rescoreEPSS 14% · 96th percentile
  10. 2026-10-13 06:26 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  11. 2026-10-12 20:35 UTCEG score recompute
  12. 2026-10-12 16:28 UTCEPSS rescoreEPSS 14% · 96th percentile
  13. 2026-10-12 07:29 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  14. 2026-10-12 03:24 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  15. 2026-10-11 23:22 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  16. 2026-10-11 19:22 UTCEG score recompute
  17. 2026-10-11 19:22 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  18. 2026-10-11 15:20 UTCEG score recompute
  19. 2026-10-11 15:20 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  20. 2026-10-11 13:40 UTCEPSS rescoreEPSS 14% · 96th percentile
  21. 2026-10-11 11:19 UTCEG score recompute
  22. 2026-10-11 11:18 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  23. 2026-10-11 07:15 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  24. 2026-10-11 03:13 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  25. 2026-10-10 23:11 UTCEG score recompute
  26. 2026-10-10 23:11 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  27. 2026-10-10 19:55 UTCEPSS rescoreEPSS 14% · 96th percentile
  28. 2026-10-10 19:09 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  29. 2026-10-10 15:06 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  30. 2026-10-10 11:04 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  31. 2026-10-10 07:02 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  32. 2026-10-10 03:02 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  33. 2026-10-09 23:00 UTCEG score recompute
  34. 2026-10-09 23:00 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  35. 2026-10-09 20:02 UTCEPSS rescoreEPSS 14% · 96th percentile
  36. 2026-10-09 18:59 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  37. 2026-10-09 14:58 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  38. 2026-10-09 10:55 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  39. 2026-10-09 06:53 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  40. 2026-10-09 02:51 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  41. 2026-10-08 22:50 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  42. 2026-10-08 18:49 UTCEG score recompute
  43. 2026-10-08 18:49 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  44. 2026-10-08 16:35 UTCEPSS rescoreEPSS 14% · 96th percentile
  45. 2026-10-08 14:48 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  46. 2026-10-08 10:43 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  47. 2026-10-08 06:42 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  48. 2026-10-08 02:40 UTCEG score recompute
  49. 2026-10-08 02:40 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  50. 2026-10-07 23:41 UTCEPSS rescoreEPSS 14% · 96th percentile
  51. 2026-10-07 22:39 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  52. 2026-10-07 18:37 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  53. 2026-10-07 14:36 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  54. 2026-10-07 10:35 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  55. 2026-10-07 06:30 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  56. 2026-10-07 02:29 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  57. 2026-10-06 22:28 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  58. 2026-10-06 18:27 UTCEG score recompute
  59. 2026-10-06 18:27 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  60. 2026-10-06 15:11 UTCEPSS rescoreEPSS 14% · 96th percentile
  61. 2026-10-06 14:26 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  62. 2026-10-06 10:25 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  63. 2026-10-06 06:24 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  64. 2026-10-06 02:23 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  65. 2026-10-05 22:22 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  66. 2026-10-05 18:17 UTCEG score recompute
  67. 2026-10-05 18:17 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  68. 2026-10-05 17:38 UTCEPSS rescoreEPSS 14% · 96th percentile
  69. 2026-10-05 14:16 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  70. 2026-10-05 10:14 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  71. 2026-10-05 06:14 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  72. 2026-10-05 02:13 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  73. 2026-10-04 22:11 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  74. 2026-10-04 18:10 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8
  75. 2026-10-04 14:08 UTCGHSA enrichmentGHSA-q8rh-r33q-hvj2 · GitHub severity CRITICAL · GitHub CVSS 9.8

Frequently asked(6)

What is CVE-2017-12240?
CVE-2017-12240 is a critical-severity vulnerability; its CVE record was 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 made public?
CVE-2017-12240 was made public on September 28, 2017: that is the date its CVE record's CNA, Cisco Systems, Inc., gives for when the vulnerability was made public. The CVE record itself was published on September 29, 2017. EchelonGraph's copy of the record carries a last-modified date of June 17, 2026; the record at its source may have been updated since.
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 attention. No fix has been recorded since the CVE record was published in 2017. Restrict network exposure of the affected system or apply the vendor's mitigation, and check the vendor's advisory for a fix.
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.
How do I remediate CVE-2017-12240?
No fix for CVE-2017-12240 has been recorded since its CVE record was published in 2017. Restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and check the vendor's advisory for a fix. The CVE record's description, written by its CNA (Cisco Systems, Inc.), states the affected versions: "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 affec…" No release containing a fix is confirmed on record.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2017-12240

Explore →

Is Your Infrastructure Affected by CVE-2017-12240?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.