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Greyhound Critical Vulnerabilities - Road Rewards Program

Gauge reading critical severity


Note: A full-length proof of concept is intentionally not being disclosed in the below advisory. 

Advisory Summary

Product Vendor

Greyhound Lines Inc. (owned by FirstGroup America Inc. – a subsidiary of FirstGroup Plc (UK))

Product Description

Greyhound Lines Inc. (U.S.) provides intercity bus service across North America. It provides a personal ticketing kiosk services via its web and mobile applications for Greyhound customers. These applications help customers manage e-ticketing, mobile check-in, and the program.

Vulnerability Details

Critical vulnerabilities were identified in the Greyhound APIs primarily due to insufficient authentication controls. Exploitation of these can result in the exposure of personally identifiable information (PII) for the customers who had joined the Road Rewards program. Additionally, an attacker can also remotely exploit an internet-exposed web service that hosts account information for Greyhound customers as well as other sensitive information. An attacker could use this vulnerability to gain access unrestricted access and completely take over user accounts belonging to affected members.

As the time of this disclosure, this vulnerability affects at least a million members.


The impact of these discovered vulnerabilities is as follows. When exploited, attackers can perform the following:

  • Hijack (take over the accounts) of more than a million people’s Greyhound Road Rewards accounts
  • Use that information to access and update users’ personal information, such as personal addresses and contact information like email addresses and phone numbers
  • View and update upcoming trips as well as users’ travel preferences (e.g., if a user frequently travels alone)

Disclosure Timeline:

  • 12/08/2018: Initial discovery
  • Vendor contacted multiple times, no response
  • 01/23/2019: Issue reported to US-CERT
  • 02/19/2019: FirstGroup Plc made contact via Greyhound support
  • 03/01/2019: Full vulnerability details disclosed to vendor
  • No vendor follow-up and is no longer responsive (The vulnerabilities are still not fixed)
  • 04/11/2019: Partial details for the vulnerabilities disclosed publicly


Priyank Nigam, Senior Security Analyst at Bishop Fox

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Priyank nigam

About the author, Priyank Nigam

Senior Security Consultant

Priyank Nigam (OSCP, OSWP, GCFE) is a Senior Security Consultant at Bishop Fox. He focuses on source code reviews, web and mobile application penetration testing, and network security. As a researcher, he is interested in all things offensive security, reverse engineering, mobile security, Internet of Things.
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