DB Ticket Vending Machine WinXP - Privilege Escalation
Vulnerability Magazine: https://www.vulnerability-db.com/?q=articles/2019/12/13/zero-day-vulnerability-deutsche-bahn-ticket-machine-series-system-uncovered
Vulnerability Laboratory ID (VL-ID):
Common Vulnerability Scoring System:
Current Estimated Price:
5.000€ - 10.000€
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)
No authentication (guest)
No User Interaction
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.
[+] Windows XP
[+] 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.
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)
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
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.
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