US-CERT: Belkin Wi-Fi Router Has a Slew of Flaws

US-CERT is warning that Belkin Wi-Fi routers contain multiple vulnerabilities—and that users should implement workarounds immediately.

Specifically, the model affected is the Belkin N600 DB Wireless Dual Band N+ router model F9K1102 v2 with firmware version 2.10.17 and possibly earlier. The flaws would allow attacks that run the gamut from arbitrary file injection to man-in-the-middle attacks to cross-site request forgery (CSRF).

Taken together, the impact is profound. “A remote, unauthenticated attacker may be able to spoof DNS responses to cause vulnerable devices to contact attacker-controlled hosts or induce an authenticated user into making an unintentional request to the web server that will be treated as an authentic request,” US-CERT said in its advisory. “A LAN-based attacker can bypass authentication to take complete control of vulnerable devices.”

For example, DNS queries originating from the Belkin N600, such as those to resolve the names of firmware update and NTP servers, use predictable TXIDs that start at 0x0002 and increase incrementally. An attacker with the ability to spoof DNS responses can cause the router to contact incorrect or malicious hosts under the attacker's control.

Also, Belkin uses HTTP by default for checking and transmitting firmware update information to vulnerable routers. An attacker capable of conducting man-in-the-middle attacks can manipulate traffic to block updates or inject arbitrary files.

Belkin N600 by default does not set a password for the web management interface. A local area network (LAN) attacker can gain privileged access to the web management interface or leverage the default absence of credentials in remote attacks such as cross-site request forgery.

When a password is implemented in the Belkin N600 web management interface, authorization is enforced client-side by the browser. By intercepting packets from the embedded server, an attacker can bypass authentication and gain full, privileged access to restricted pages of the web management interface.

And finally, Belkin N600 routers contain a global CSRF vulnerability. An attacker can perform actions with the same permissions as a victim user, provided the victim has an active session and is induced to trigger the malicious request. Note that in default configurations lacking password protection, an attacker can establish an active session as part of an attack and does not require a victim to be logged in.

The vulnerabilities have not been addressed, so users should restrict access and only allow trusted hosts to connect to the LAN. Users should also use strong passwords, and LAN hosts should not browse the Internet while the web management interface has an active session in a browser tab.

“Note that there are no practical workarounds for the DNS spoofing or firmware over HTTP issues, as general users are unlikely to be able to monitor traffic entering the router's WAN port,” the advisory concluded.

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