CVE-2026-66747

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-05. a secondary CVSS source baseline 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: Elevated riskExposed: 0

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

Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds. Its command handler passes any received string to popen() as uid=0, and a reserved rctlbash command returns an interactive root shell. Because the channel is unauthenticated and cleartext, control is not limited to whoever planted it: any party that answers at the C2 address, occupies the network path (DNS or route hijack), or acquires the hardcoded fallback domain obtains unauthenticated remote code execution as root.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
75(Attend)
EG Risk 75/100SSVC: Attend

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%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
50%
KEV
Not listed

Published

August 5, 2026

Last Modified

September 9, 2026

Advisory Details (4)

Auto-updated Sep 16, 2026
No patch confirmed yet.
generic

ZBT router firmware download – Zbtlink Online Store

https://www.zbtlink.com/pages/zbt-router-firmware-download
generic

ENDLESSDOORS Is Phoning Home. Pick Up. | Blog | VulnCheck

https://www.vulncheck.com/blog/zbt-endlessdoors
generic

ENDLESSDOORS: Zbtlink Router rctl/kworker Phone-Home Root Implant | Advisories | VulnCheck

https://www.vulncheck.com/advisories/zbt-endlessdoors
generic

GitHub - ycsunjane/rctl: remote linux control · GitHub

https://github.com/ycsunjane/rctl

Vendor Advisories for CVE-2026-66747(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 42× in last 7d / 182× 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 301 total refreshes for this CVE.

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

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 GitHub PoC). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCoiehnow/oieh-router-checker
    First seen Aug 22, 2026

    내 공유기가 Zbtlink ENDLESSDOORS 백도어(CVE-2026-66747) 대상인지 클릭 한 번으로 검사하는 Windows 프로그램

    Open source ↗

Frequently asked(5)

What is CVE-2026-66747?
CVE-2026-66747 is a critical vulnerability published on August 5, 2026. Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in…
When was CVE-2026-66747 disclosed?
CVE-2026-66747 was first published in the National Vulnerability Database on August 5, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-66747 actively exploited?
CVE-2026-66747 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 50.0% of all scored CVEs.
What is the CVSS score of CVE-2026-66747?
CVE-2026-66747 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-66747?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-66747, 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.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-66747

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