Security Advisory AA-001

Authentication Bypass Vulnerability in Conceptronic Grab’n’Go Network and Sitecom Home Storage Center

Security Advisory AA-002

Password disclosure Vulnerability in Conceptronic Grab’n’Go and Sitecom Home Storage Center

Security Advisory AA-003

Directory Traversal Vulnerability in Conceptronic Grab’n’Go Network Storage (0-day)

Security Advisory AA-004

Directory Traversal Vulnerability in Sitecom Home Storage Center

Security Advisory AA-005

Authorization Bypass Vulnerability in Password Reset Function Conceptronic Grab’n’Go Network Storage (0-day)

Security Advisory AA-006

Authorization Bypass Vulnerability in Password Reset Function Sitecom Home Storage Center

Security Advisory AA-007

Security Advisory AA-007: Arbitrary File Upload Vulnerability in Sitecom Home Storage Center

Security Advisory AA-008

Command Injection Vulnerability in Sitecom Home Storage Center

Responsible Disclosure

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Security Advisory AA-002: Password disclosure Vulnerability in Conceptronic Grab’n’Go and Sitecom Home Storage Center

Vulnerability Type

Password disclosure

Severity

Alcyon rates the severity of this vulnerability as high due to the following properties:

  • Ease of exploitation;
  • No authentication credentials required;
  • No knowledge about individual victims required;
  • No interaction with the victim required.
  • Conceptronic CH3ENAS, firmware version 3.0.8 and below
  • Conceptronic CH3HNAS, firmware version 2.4.11 and below
  • Sitecom MD-253 and MD-254, firmware version 2.4.11 and below

Products and firmware versions affected

Our investigation showed that the mentioned products originate from the Taiwanese manufacturer Mapower. Possibly other rebranded Mapower network storage products are also affected by this flaw.

Dates

  • Discovery on May 5, 2012
  • Vendor notification on May 31, 2012
  • Fix available since July 27, 2012
  • Public disclosure on August 27, 2012

Risk Assessment

An attacker can harvest administrator credentials and log into the web management UI. Possibilities include but are not limited to reading and writing files stored on the device and altering the device’s configuration.

This means an attacker could:

  • Steal sensitive data stored on the device;
  • Leverage the device to drop and/or host malware;
  • Abuse the device to send spam through the victim’s Internet connection;
  • Use the device as a pivot point to access locally connected systems or launch attacks directed to other systems.

An investigation on our part shows that a multitude of affected devices are directly accessible through the Internet. It appears that this type of NAS-device is popular amongst small businesses. We have seen examples of video production companies and copy shops that utilize this device for file sharing purposes with their customers. Other cases of exposure seem to be unintentional. Since some ISP’s assign multiple public IP-addresses to their customers, devices that are connected to the router obtain an Internet-routable IP-address.

Vulnerability

The web management UI validates the user’s login credentials through a JavaScript routine that queries hidden page elements:

function LoginSubmit(){
  var data = document.getElementById("Users").value;
  data = data.split(":");
  var UserName = document.getElementById("UserName").value;
  var UserPasswd = document.getElementById("UserPasswd").value;
  if((UserName==data[0])&&(UserPasswd==data[1])){
    document.cookie = "2L:CH3HNAS"
    location.replace ('index.html');
} else {
  document.getElementById("UserName").value = '';
  document.getElementById("UserPasswd").value = '';
  alert(getWord("login_unauthorized"));
    setTimeout(function(){document.getElementById("UserName").focus();},10);
    return false;
}

if(document.cookie.indexOf("2L:CH3ENAS")
 location.replace ('login.htm');
}

While client side validation and relying on a static session token are weaknesses in themselves (please refer to advisory AA-001), an additional risk of password disclosure is present in the affected firmware versions.

These hidden elements are populated by two different JavaScript functions found in login.js:

function Login(){
  getContent('','/cgi-bin/login.cgi?webmaster',"function:showLogin");
}

function showLogin(msg){
     msg = msg.split("\n");
     window.document.getElementById('data').innerHTML = '';
     setTimeout(function(){document.getElementById("UserName").focus();},10);
}

The getContent function is responsible for querying a URL and passing the result to the showLogin function. In this case the result of the web request consists of the username and password of the admin user in clear text form.

Proof of Concept

Paste the following URL into a web browser’s address bar to obtain the administrator’s username and password:

http://cgi-bin/login.cgi?webmaster&1&Conceptronic2009

Risk Mitigation

Updating your NAS firmware to the latest version will protect you from this particular attack, but the presence of this type of flaw and the vendors’ responses seem to be an indication for a lack of security awareness on their part.

Unfortunately, for owners of similar, other branded products originating from Mapower, a patched firmware version may be unavailable at this time.

We recommend that you limit access to the web management UI of the device by utilizing proper packet filtering and/or NAT on your router in order to limit network access to your NAS. Although this will not completely eliminate the risk of exploitation, it becomes substantially more difficult to leverage a successful attack, because it would involve either a compromise of another host on the victim’s local network or a client side attack that overcomes the Same Origin Policy restrictions of the victim’s web browser.

Vendor responses

2L/Conceptronic acknowledged the presence of this flaw in the particular model and firmware version we reported, but did not disclose details on other products affected. Instead, the same flaw was silently patched in the firmware of a similar product. Updated firmware is available on the Conceptronics’s website since July 27, 2012. The vendor did not coordinate the release of this firmware update with us.

As soon as our investigations pointed out that the affected devices originated from the Taiwanese manufacturer Mapower, we tried to contact them directly. Mapower neither has confirmed or denied the reported flaw. Interestingly, the same fix they provided to 2L/Conceptronic was already present in Sitecom’s latest firmware and yet they had not notified 2L/Conceptronic about the flaw at that time. It took Mapower more than 2 months after our initial report to supply 2L/Conceptronic with the same fix.

Fix

The vendors have update their firmware to address this issue: