Researchers Discover Hidden Backdoor in 20 Router Models Allowing Remote Root Access

VulnCheck researchers discovered a built‑in backdoor (named ENDLESSDOORS) in 20 Zbtlink-based router models that automatically phones home to hardcoded command servers and executes any received commands as root (including spawning an interactive root shell); the implant is vendor-supplied, present across multiple rebranded devices, connects to four known endpoints hosted on cloud providers, and there is no available patch—affected devices should be treated as compromised and replaced or isolated.