CVE-2026-66747

CRITICALPre-NVD 9.89.8—
EchelonGraph scoreHIGH 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(high)
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
45%
KEV
Not listed

Published

August 5, 2026

Last Modified

August 5, 2026

Advisory Details (4)

Auto-updated Aug 19, 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 55× in last 7d / 128× 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 128 total refreshes for this CVE.

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

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. 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 54.8% 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.

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