CVE-2026-66747: Zbtlink CPE2801 Firmware vulnerability

1. In CISA KEV: not seen
2. Exploited (reported): not seen
3. Scanning observed: not seen
4. Proof of concept public1 public GitHub repository (unverified), listed by PoC-in-GitHub22 Aug
5. Not established: not seen

DescriptionNVD

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.

Exploitation

Unlikely (under 1%). EPSS under 1%, or no score yet.

CISA KEV

Not listed

Public check

No public nuclei template

Weakness

Embedded Malicious Code · Supply Chain and Malicious Code

Published

August 2026

Band

Unlikely (under 1%), August 2026

1. 22 Aug
   PoC-in-GitHub lists 1 public GitHub repository (unverified) PoC-in-GitHub

• NVD entrynvd.nist.gov
• Vendor advisoryvulncheck.com
• CVE recordcve.org
• Weakness CWE-506cwe.mitre.org