Asus Patches Vulnerabilities in RT Routers

Asus Patches CSRF, JSONP and XSS Flaws in RT Routers

Asus RT-AC and RT-N devices that are not running the latest firmware version are vulnerable to a series of CSRF, JSONP and XSS vulnerabilities that allow malicious actors to disclose information, change device settings, or inject code.

Asus addressed the flaws in its March 2017 firmware update (which arrived on devices as version 3.0.0.4.380.7378), but some details have been published only this week. According to Nightwatch Cybersecurity researchers, multiple issues affect the web interface RT routers arrive with, although it is normally accessible only from LAN and not from the Internet.

The vulnerabilities, the researchers say, “can facilitate attacks on the router either via a malicious site visited by a user on the same network, or a malicious mobile or desktop application running on the same network.”

The release notes published by Asus on its support website show that a total of five vulnerabilities were addressed in firmware version 3.0.0.4.380.7378. Additionally, the update added log message for brute force attack and fixed various non-security bugs.

Tracked as CVE-2017-5891, the first of the bugs includes a Login Page Cross-Site Request Forgery (CSRF) and Save Settings CSRF, which allow malicious sites to login and change settings in the router. The issue is that the login page for the web interface, the same as the various pages that can save Settings, has no form of CSRF protection.

Because of that, malicious sites could submit login requests without user’s knowledge, but only as long as the site knows the username and password of the router. Devices where the default credentials (admin / admin) haven’t been replaced yet are certainly at risk. Once logged in, the site could change any settings in the router without the user’s knowledge.

Tracked as CVE-2017-5892, the second vulnerability resides in the presence of two JSONP (JSON with Padding) endpoints within the router, which allow “detection of which ASUS router is running and some information disclosure,” coupled with the existence of “multiple JSONP endpoints within the router interface that reveal various data from the router,” Nightwatch Cybersecurity says.

The exposed data includes network information, surrounding access points on both 2.4 GHz and 5GHz bands, network map of devices on the network, origin data, external IP address, and WebDAV information.

Another related issue is the presence of an XML endpoint in the router, which reveals the Wi-Fi password to the router. For exploitation, however, a mobile or desktop application running on the local network is required, because XML cannot be loaded cross origin in the browser.

The third bug is a session hijack vulnerability in HTTPD affecting RT-N and RT-AC running firmware before 3.0.0.4.380.7378, RT-AC68W routers with firmware before 3.0.0.4.380.7266; RT-N routers with firmware before 3.0.0.4.380.9488; and Asuswrt-Merlin firmware before 380.65_2. Tracked as CVE-2017-6549, the bug allows remote attackers to steal any active admin session by sending cgi_logout and asusrouter-Windows-IFTTT-1.0 in certain HTTP headers.

A fourth bug was a cross-site scripting (XSS) vulnerability in HTTPD in the aforementioned firmware versions. Tracked as CVE-2017-6547, the flaw allows remote attackers to inject arbitrary JavaScript by requesting filenames longer than 50 characters.

Finally, Asus also resolved buffer overflows (CVE-2017-6548) in networkmap on said firmware releases, which could “allow remote attackers to execute arbitrary code on the router via a long host or port in crafted multicast messages.”

Owners of affected routers should install the latest firmware release on their devices as soon as possible. They should also consider changing the default credentials, if they haven’t already.

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