HP ThinPro - Application filter bypass
===============================================================================

Identifiers
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* CVE-2019-16286

CVSSv3 score
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6.1 (AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N)

Vendor
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HP - [https://www.hp.com](https://www.hp.com)

Product
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Deliver secure desktop virtualization that’s as comfortable for IT as it is
for end users with the stunningly redesigned HP ThinPro. It has a bold new
user interface and workflow refinements that make it a breeze to configure,
manage, and use right out of the box.

Affected versions
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 - HP ThinPro Linux 7.1
 - HP ThinPro Linux 7.0
 - HP ThinPro Linux 6.2.1
 - HP ThinPro Linux 6.2

Credit
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Eldar Marcussen - xen1thLabs - Software Labs

Vulnerability summary
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The HP ThinPro allows administrators to determine what applications users
can run, however attackers can bypass these restrictions to spawn
restricted applications and run arbitrary commands on the device.

Technical details
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There are several paths to exploit this, but the most common path is to
find exploit it directly from a `Web Browser` connection, or find a
clickable link that will spawn firefox from one of the other connections.
Once in firefox the attacker can access preferences to configure which
application handles certain filetypes and use this to spawn another
application. The list of possible applications is restricted, but it is
possible to spawn `/usr/bin/hptc-kiosk` which supports creating custom
connections which can run arbitrary commands.

Proof of concept
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The following evidence is provided to illustrate the existence and
exploitation:

1. In a `Web Browser` connection open Firefox's `Preferences`
2. Select the `Applications` section
3. Locate the `Portable Document Format (PDF)` content type and select `Use
other` from the drop down menu
4. Navigate to `/usr/bin/hptc-kiosk` and press Open
5. Verify that the PDF handler is set to `Use hptc-kiosk`
6. Open a new tab and type the following in the address bar
   `data:application/pdf,pwnt!`
   and press enter
7. Observe that a `Connection manager` window now opens
8. Click on the `+` icon in the bottom right
9. Select `Custom`
10. Enter `xterm` in the textbox for command to run and click Finish
11. Select the newly created connection
12. Click the `->` icon in the bottom left corner
13. Observe xterm spawning

Solution
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Contact vendor for a solution

Timeline
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Date        | Status
------------|-----------------------------
19-AUG-2019 | Reported to vendor
22-NOV-2019 | Patch available
24-MAR-2020 | Public disclosure