Document Title:  
Deutsche Bahn Ticket Vending Machine Windows XP - Local Kiosk Privilege  
Escalation Vulnerability  
References (Source):  
Vulnerability Magazine:  
Release Date:  
Vulnerability Laboratory ID (VL-ID):  
Common Vulnerability Scoring System:  
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:  
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:  
Exploitation Technique:  
Severity Level:  
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  
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)  
Solution - Fix & Patch:  
There are now several problems related to system hardening that can be  
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  
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  
Credits & Authors:  
Benjamin K.M. -  
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