# Exploit Title: Deutsche Bahn Ticket Vending Machine Local Kiosk - Privilege Escalation
# Date: 2019-12-18
# Exploit Author: Vulnerability-Lab
# Vendor Homepage: https://www.bahn.de/db_vertrieb/view/leistungen/automaten-fahrkartenentwerter.shtml
# Tested on: Windows XP

Document Title:
===============
Deutsche Bahn Ticket Vending Machine  - Local Kiosk Privilege Escalation Vulnerability


References (Source):
====================
https://www.vulnerability-lab.com/get_content.php?id=2191

Vulnerability Magazine:
https://www.vulnerability-db.com/?q=articles/2019/12/13/zero-day-vulnerability-deutsche-bahn-ticket-machine-series-system-uncovered


Release Date:
=============
2019-12-14


Vulnerability Laboratory ID (VL-ID):
====================================
2191


Common Vulnerability Scoring System:
====================================
6.4


Vulnerability Class:
====================
Privilege Escalation


Product & Service Introduction:
===============================
Customers can buy tickets at our ticket machines at any time, regardless
of opening hours. Thus, the vending machine also
secures sales in rural areas.

- innovatively designed user guidance
- Real-time timetable information for rail traffic
- traveler information
- ticket paper supply
- free fault hotline: 0800 2886644
- Professional and contemporary maintenance

The ticket vending machine can also be configured according to
individual requirements. The housing can be designed as desired.
Customers can purchase their tickets with different means of payment.
User guidance is available in different languages.

(Copy of the Homepage:
https://www.bahn.de/db_vertrieb/view/leistungen/automaten-fahrkartenentwerter.shtml
)


Abstract Advisory Information:
==============================
The vulnerability laboratory core research team discovered a local kiosk
privilege escalation vulnerability in the deutsche bahn ticket vending
machine series with windows xp.


Vulnerability Disclosure Timeline:
==================================
2019-12-14: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Exploitation Technique:
=======================
Local


Severity Level:
===============
Medium


Authentication Type:
====================
No authentication (guest)


User Interaction:
=================
No User Interaction


Disclosure Type:
================
Responsible Disclosure Program


Technical Details & Description:
================================
A kiosk mode escalation vulnerability has been discovered in the
official deutsche bahn ticket vending machine series for windows.
The security vulnerability allows local attackers to bypass the kiosk
mode to compromise the local file system and applications.

It is possible for local attackers to break out of the kiosk mode of the
Deutsche Bahn vending machine application if
the Password Agent (PasswordAgent.exe) of the system receives a timeout
or has a runtime error in the program
itself in the background. These errors can occur due to aborted
sessions, unclean logout or common errors when
using the application at system level.

In the event of a local error, attackers can bring the error message to
the foreground by pressing the number field - Cancel
during a transaction. After the error message becomes visible, the
attacker can click on a link of the error message where you
can normally see what the error report contains. The attacker will then
be redirected to a form in the error message, where he
can search for errors in a collection of microsoft articles via "Submit
/ Dont' Submit" or another link on the online path. There
the attacker clicks on it and receives the web browser. From the web
browser, the attacker retrieves the options menu and can access
the local system directory and has then the ability to compromise the
ticket vending machine with windows xp.

The error message is normally on those devices deactivated through a
hardening process of the servce provider. In that special case
the exception handling of windows was not deactivated or set to the
background, which allows the attacker to move through to other
options to finally access the file system via browser.

The ticket vending machine vulnerability requires no user interaction
and can only be exploited by local attackers with physical
device access. No keyboard or front loader opening required.


Vulnerable System(s):
[+] Windows XP

Affected Component(s):
[+] Exception Handling (Error Message Content)


Proof of Concept (PoC):
=======================
The local vulnerability can be exploited by local attackers with
physical device access without user interaction.
For security demonstration or to reproduce the vulnerability follow the
provided information and steps below to continue.


PoC: Sheet
PasswordAgent.exe := Unexpected Error (Background) - Runtime/Session/Timeout
=> Transaction Application => Cancel := Unexpected Error (Background) -
Runtime/Session/Timeout (Front)
=> Click Error Report => Click Search Collection => Web Browser => Local
File System => PWND!


What are attackers able to do when the file system of the vending
machine is accessable thus way?
1. Inject of local malware to the ticket machine (editor / debugger /
cmd / ps - exp. ransomware/malware)
2. Local manipulation for skimming devices to assist (transmit prepares)
2. Phishing of local credentials from screen via system (db browser
application)
3. Intercept or manipulation to access card information (local file
system - sniff/extract)
4. Crash or freeze the computer system (exp. kill of process / loop script)
5. Scare or joké activities (exp. html / js to front screens with web
browser or by a new window process)

Refernece(s):
https://www.vulnerability-db.com/sites/default/files//newscenter-gallery/IMG_6457.JPG
https://www.vulnerability-db.com/sites/default/files//newscenter-gallery/IMG_6458.JPG
https://www.vulnerability-db.com/sites/default/files//newscenter-gallery/IMG_6460.JPG


Solution - Fix & Patch:
=======================
There are now several problems related to system hardening that can be
resolved:
1. It should not be possible for users with system user rights to use
the web browsers
2. The error message menu can be deactivated or completely modified
3. Some functions in menus can be deactivated by hardening (browser,
messages & Co.)
4. Check that all other tasks are always running in the background or
are being moved there permanently
5. The deutsche bahn vending machine application and user interface
should be shut down in the event of persistent errors in the foreground
6. The activities of the testing has been logged but did not triggered
any alert for defense purpose


Deutsche Bahn: Patch Rollout in Progress
https://www.vulnerability-db.com/sites/default/files//newscenter-gallery/073915298_0.png

https://www.vulnerability-db.com/sites/default/files//newscenter-gallery/dbatm78235.png


Security Risk:
==============
The security risk of the local ticket vending machine system
vulnerability is estimated as high.  The bug to escalate can be easily
exploited by local interaction with the touch display to access the file
system.


Credits & Authors:
==================
Benjamin K.M. -
https://www.vulnerability-lab.com/show.php?user=Benjamin+K.M.


Disclaimer & Information:
=========================
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