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SEC Consult SA-20170307-0 :: Unauthenticated OS command injection & arbitrary file upload in Western Digital WD My Cloud

SEC Consult Vulnerability Lab Security Advisory < 20170307-0 >
              title: Unauthenticated OS command injection & arbitrary file upload
            product: Western Digital My Cloud
 vulnerable version: at least: 2.21.126 (My Cloud), 2.11.157(My Cloud EX2),
                     2.21.126 (My Cloud EX2 Ultra), 2.11.157 (My Cloud EX4),
                     2.21.126 (My Cloud EX2100), 2.21.126 (My Cloud EX4100),
                     2.11.157 (My Cloud Mirror), 2.21.126 (My Cloud Mirror
                     Gen2), 2.21.126 (My Cloud PR2100), 2.21.126 (My Cloud
                     PR4100), 2.21.126 (My Cloud DL2100), 2.21.126 (My Cloud
      fixed version: -
         CVE number: -
             impact: Critical
           homepage: https://www.wdc.com/en-um/
              found: 2017-01-17
                 by: Wan Ikram (Office Kuala Lumpur)
                     Fikri Fadzil (Office Kuala Lumpur)
                     SEC Consult Vulnerability Lab

                     An integrated part of SEC Consult
                     Bangkok - Berlin - Linz - Luxembourg - Montreal - Moscow
                     Kuala Lumpur - Singapore - Vienna (HQ) - Vilnius - Zurich



Vendor description:
"Reliable, centralized personal storage with automatic backup that plugs into
your own home network. Share whatever you want, anywhere you have an Internet

Source: https://www.wdc.com/products/personal-cloud-storage/my-cloud.html

Business recommendation:
By combining the vulnerabilities documented in this advisory an attacker
can fully compromise a WD My Cloud device. In the worst case one could steal
sensitive data stored on the device or use it as a jump host for further
internal attacks.

SEC Consult recommends not to attach WD My Cloud to the network until
a thorough security review has been performed by security professionals and
all identified issues have been resolved.

Vulnerability overview/description:
The firmware doesn't apply proper validation on many user inputs. As a
result, below vulnerabilities could be exploited by unauthenticated attackers
to fully compromise the device.

1. Unauthenticated OS Command Injection
Any OS commands can be injected by unauthenticated attackers. This is a
serious vulnerability as the chances for the device to be fully compromise is
very high.

2. Unauthenticated Arbitrary File Upload
A malicious file can be uploaded into the webserver with no authentication
required. It is possible for an attacker to upload a script to issue operating
system commands.

3. Cross Site Request Forgery (CSRF)
There is no anti-CSRF mechanism implemented in the firmware. Due to this, an
attacker can force a user to execute any action through any script. As the
vulnerabilities described in 1) and 2) do not need authentication, those can
be exploited via CSRF over the Internet as well!

Proof of concept:
1. Unauthenticated OS Command Injection
Below is a sample cURL request to execute arbitrary OS command for one of
vulnerable scripts.

$ curl
<os-command-here>\; echo \"x

2. Unauthenticated Arbitrary File Upload
Below is the cURL request to upload arbitrary files on the webserver.

$ curl -F "file=@shell.php"

3. Cross Site Request Forgery (CSRF)
There is no anti-CSRF mechanism implemented for all accessible scripts in the

Vulnerable / tested versions:
The following device & firmware has been tested and found to be vulnerable:
2.11.157 (My Cloud EX2)

As the firmware used by all My Cloud devices are more or less similar, we
believe the other versions are also prone to the same vulnerabilities. This could
be verified by using the IoT Inspector software for automated firmware analysis.

Vendor contact timeline:
2017-01-18: Contacting vendor through "WD Support - Create a Support Case"
            page (https://support.wdc.com/support/case.aspx?lang=en).
            Assigned ticket number - 011817-11728265.
2017-01-19: Vendor: replies to the ticket asking for more clarification.
2017-01-20: Replied to the vendor, requesting security contact and encryption keys
2017-01-23: Vendor: "we don't have a security department that we could forward
            this concern"
2017-01-23: Telling support that there seems to be a security contact by
            referencing other WD advisories, requesting security contact again
2017-01-24: Vendor: asking for affected product name and firmware version.
2017-01-24: Providing list of affected product name and firmware versions,
            requesting security contact again
2017-01-25: Vendor: informs us that they "have already escalated the case from
            their back end team", they will update us.
2017-02-09: Requesting a status update
2017-02-10: Vendor (support): back end team is already informed, they will follow
2017-02-10: Vendor security contact emails us
2017-02-16: Asking for encryption information to send advisory
2017-02-16: Vendor (security contact): requests security advisory to be shared
            over unencrypted channel
2017-02-20: Provided advisory and proof of concept through insecure channel as
2017-02-21: Vendor (security contact): requesting extension of deadline to a
            period of 90 days from the date of detail disclosure
2017-02-22: Informing the vendor that we grant extension of disclosure but not
            from detail disclosure date (2017-02-20), but from initial contact
            date (2017-01-18) as they could have reacted faster in the first place
            Set latest disclosure date to 2017-04-19 (no answer from vendor)
2017-03-03: 3rd party researcher discloses many 0-days, containing our findings as
            well, https://www.exploitee.rs/index.php/Western_Digital_MyCloud
2017-03-07: Informing vendor security contact of our public disclosure
2017-03-07: Public disclosure of advisory

There is currently no update available from the vendor.


Advisory URL:


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EOF Fikri Fadzil / @2017

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