GhostMail - (Filename to Link) Cross Site Web Vulnerability

Type vulnerlab
Reporter Vulnerability-Lab [] -
Modified 2018-06-26T00:00:00


                                            Document Title:
GhostMail - (Filename to Link) Cross Site Web Vulnerability

References (Source):

Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

Vulnerability Class:
Cross Site Scripting - Persistent

Current Estimated Price:
500€ - 1.000€

Product & Service Introduction:
Sign up to military grade encrypted GhostMail and enjoy instant free and secure email & chat. No download or installs needed.
GhostMail is your new secure email & chat platform, with great features like self destruction, two factor login and much more...
Join free today and start enforcing your privacy and online rights.

(Copy of the Vendor Homepage: )

Abstract Advisory Information:
The vulnerability laboratory core research team discovered an application-side vulnerability in the official GhostMail chat online service web-application.

Vulnerability Disclosure Timeline:
2018-06-26: Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Affected Product(s):
GhostCom Ltd.
Product: GhostMail (Chat) - Web Application (Online Service) 2015 Q2

Exploitation Technique:

Severity Level:

Authentication Type:
Restricted authentication (user/moderator) - User privileges

User Interaction:
Low User Interaction

Disclosure Type:
Bug Bounty Program

Technical Details & Description:
An application-side input validation web vulnerability has been discovered in the official Ghostmail online service web-application.
The vulnerability allows remote attackers to inject own script codes on the application-side of the affected web-application module.

The vulnerability is located in the `file attach link` and `filename` value of the `ghostmail - mail` module. The filename and 
file attach link input values are wrong encoded. The vulnerability allows remote attackers to inject own script code to the 
application-side of the vulnerable module. The request method to inject the script code is POST and the attack vector is persistent.

The security risk of the persistent web vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 3.7.
Exploitation of the persistent input validation vulnerability requires a low privileged web-application user account and low user interaction. 
Successful exploitation results in session hijacking, persistent phishing attacks, persistent external redirect and malware loads or persistent 
manipulation of affected and connected module context.

Request Method(s):
[+] POST

Vulnerable Module(s):
[+] Ghostmail/mail

Vulnerable Input(s):
[+] File attach link

Vulnerable Parameter(s):
[+] filename

Proof of Concept (PoC):
The application-side web vulnerability can be exploited by remote attackers with low privileged application user account and low user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.

PoC: Payload (Exploitation)
<a href="blob:" download="" filename="../"[MALICIOUS SCRIPT CODE PAYLOAD!]">"></a>

Manual steps to reproduce the security vulnerability ...
1. Opne the ghostmail online service page and login
2. Move to the ./mail path of the application
3. Start a session tamper for http protocols to intercept
4. Inject your own script code in the name of attach file parameter during the request
Note: There's a script code injection vulnerability in the link for the file attach (attachment) parameter
Note: In the link to download the file and in the download="name file" use "title="THIS IS A VULN_LAB TEST"
5. When you will upload a file with name "filename=" 
6. The link in the attachment changes and cannot download the file because the link has no name specification for downloading
Note: <a href="blob:" download="" filename="[MALICIOUS SCRIPT CODE PAYLOAD!]>"></a>
7. Successful reproduce of the vulnerability!


Solution - Fix & Patch:
The vulnerability can be patched by a parse and encode of the vulnerable filename and link to filename value in the upload POST method request.
Restrict the input and disallow special chars. Escape the web context to prevent an application-side script code execution vulnerability.

The vulnerability has been reported 2016-10-01. The issue was resolved during the 2017 Q2 - Q4 by the ghost mail developer team.

Security Risk:
The security risk of the application-side input validation web vulnerability in the ghostmail mail module is estimated as medium (CVSS 4.2).

Credits & Authors:
Vulnerability-Lab [] -

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