CVE-2026-66747

CVE Enrichment

CVSS: 9.3 CRITICAL
EPSS: 0.79%
EPSS Percentile: 55.75%
CISA KEV: Not listed

Description

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.

Technical Details

CVSS Version: 4.0
CNA / NVD Source: [email protected]
Published: 05-Aug-2026 18:16
Last Modified: 10-Sep-2026 03:35
EPSS Date: 2026-10-22
CWE: CWE-506

CVSS Vector


            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 /
                            E:X /
                            CR:X /
                            IR:X /
                            AR:X /
                            MAV:X /
                            MAC:X /
                            MAT:X /
                            MPR:X /
                            MUI:X /
                            MVC:X /
                            MVI:X /
                            MVA:X /
                            MSC:X /
                            MSI:X /
                            MSA:X /
                            S:X /
                            AU:X /
                            R:X /
                            V:X /
                            RE:X /
                            U:X

References

Last enrichment sync: 23-Oct-2026 07:34
Sources: NVD · FIRST EPSS · CISA KEV
Latest successful provider update; providers refresh independently.

Reported Context (1)

firmware images from the Chinese company were found to contain another backdoor called ENDLESSDOORS (CVE-2026-66747, CVSS score: 9.3) that’s designed to start automatically and attempt to beacon to Chinese Weekly Cybersecurity Roundup: QTYF Disruption, AI-Agent Breach, ZBT Router Backdoors

CVE (4)

Malware (10)

People (3)

Threat Actors (5)

MITRE ATT&CK (11)

Vendors (8)

Products (9)

Tools (4)

Industries (3)

Countries (6)

Note: Related entities, including threat actors, malware, CVEs, MITRE ATT&CK techniques, vendors, products, tools, countries, and industries, are shown when they appear in the same reporting. Their presence does not necessarily mean they were targeted, compromised, vulnerable, responsible for the activity, or directly involved in the incident.