---
cve: "CVE-2026-66747"
severity: "CRITICAL"
cvss: 9.3
epss: "58%"
vendor: "Zbtlink"
kev: false
exploited: false
published: "2026-08-05 10:50:45"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-02T03:09:06+02:00"
---

# CVE-2026-66747

> 9.3 CRITICAL · 🧪 PoC

## Beschreibung

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-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Referenzen

- <https://www.vulncheck.com/blog/zbt-endlessdoors>
- <https://www.zbtlink.com/pages/zbt-router-firmware-download>
- <https://github.com/ycsunjane/rctl>
- <https://www.vulncheck.com/advisories/zbt-endlessdoors>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-66747) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_