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 mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.8%CVSS: 9.8Exploit: Elevated riskExposed services: Not assessed

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

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
9.8CRITICALmedium confidence
EG Risk
75
EG Risk 75/100CISA SSVC

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%
CISA SSVC: Track at low, Track* at medium and Attend at high mission impact.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
0.8%
EPSS %ILE
54th
KEV
Not listed

CISA SSVCTrack at low, Track* at medium and Attend at high mission impact.

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 5, 2026

Last Modified

September 9, 2026

Advisory Details (4)

Auto-updated Sep 30, 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 21× in last 7d / 140× 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 358 total refreshes for this CVE.

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

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 ↗

Related CVEs(same CWE)

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 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 0.8% probability of exploitation in the next 30 days (54th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-66747?
CVE-2026-66747 has a CVSS base score of 9.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-66747?
No fix for CVE-2026-66747 is confirmed yet. Until one is published, 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 watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-66747 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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

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