HP ThinPro - Citrix command injection
===============================================================================

Identifiers
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* CVE-2019-18909

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 Citrix receiver conection wrapper function does not safely handle user
supplied data allowing an unauthenticated attacker to use commandline
syntax to execute arbitrary commands on the device.

Technical details
------------------------------------------------
The user supplied values provided for the domain portion of the login
screens for `Citrix receiver` is vulnerable to command injection, an
unauthenticated attacker can exploit this to execute commands with the
privileges of the local user.

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

1. At the `Citrix receiver` login screen enter the following details:
  * username: \pwnt
  * password: pwnt
  * Domain should be empty
2. Click `Connect`
3. In the `Citrix server details` window, enter the following for domain:
   `;xterm;echo `
4. Click `Connect`
5. Observe that xterm spawns

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