^{CVE-2020-23648:}Authentication Bypass Vulnerability in Asus RT-N12E Router

Overview

The vulnerability in Asus RT-N12E routers (firmware version 2.0.0.39) stems from improper access control implementation. The router's web interface fails to properly validate user authentication before allowing access to critical administrative functions. Specifically, the system.asp and start_apply.htm pages can be accessed directly, bypassing authentication requirements. An attacker can exploit this vulnerability to change the administrator password, gaining full control over the router's configuration. This type of vulnerability is classified as CWE-306 (Missing Authentication for Critical Function). Once exploited, attackers can modify network settings, redirect traffic, conduct man-in-the-middle attacks, or use the compromised router as a pivot point for further network intrusion.

Remediation

1. Update router firmware immediately to the latest version available from the official Asus website.
2. If no security patches are available, consider implementing these temporary mitigations:
   • Change the default router administration port from 80/443 to a non-standard port
   • Restrict administration access to specific trusted IP addresses
   • Implement a strong password policy
   • Disable remote management if not required
   • Consider placing the router behind another security device if possible
3. Regularly check the Asus support website for firmware updates
4. Monitor router logs for suspicious activities
5. Consider replacing the device with a newer model that receives regular security updates if Asus no longer supports this model with security patches

References

1. Vulnerability details and exploit: https://gist.github.com/ninj4c0d3r/574d2753d469e4ba51dfe555d9c2d4fb
2. Asus RT-N12E firmware download page: https://www.asus.com/Networking/RTN12E/HelpDesk_BIOS/
3. Shodan search for potentially vulnerable devices: https://www.shodan.io/search?query=rt-n12e
4. CWE-306: Missing Authentication for Critical Function: https://cwe.mitre.org/data/definitions/306.html