Trustwave SpiderLabs Security Advisory TWSL2021-009:
Persistent Cross-Site Scripting in SolarWinds Serv-U FTP Server

Published: 07/02/2021
Version: 1.0

Vendor: SolarWinds (www.solarwinds.com)
Product: SolarWinds Serv-U FTP Server
Version affected: 15.2.2

Product description:
SolarWinds Serv-U FTP Server is a file transfer software.

Finding 1: SolarWinds Serv-U FTP Server Persistent Cross-Site Scripting
*****Credit: Victor Kahan of Trustwave 
CVE: CVE-2021-32604
CWE: CWE-79

Affected versions do not properly sanitise and validate the user-supplied
'SenderEmail' parameter, allowing malicious Javascript to be injected into a
publicly shareable URL.

Proof of concept
----------------
1. Authenticate to the Serv-U web server as a user with any form of privilege.

2. Navigate to https://serverhost/Web Client/Share/IncomingWizard.htm

3. Populate and submit the form with any data.

4. Capture the request in an interception tool and modify the ‘SenderEmail’ parameter, eg.
   "'/><script>alert(7)%3b</script>%40localhost.local

5. Retrieve the ‘ShareURL’ parameter from the response body.

6. Navigate to the publicly accessible ‘ShareURL’ and observe the injected payload.

Remediation Steps:
Upgrade to Serv-U 15.2.3 or the latest stable version.

Revision History:
02/22/2021 - Vulnerability disclosed to vendor
05/05/2021 - Serv-U FTP Server released
07/02/2021 - Advisory published

References
1. https://documentation.solarwinds.com/en/success_center/servu/content/release_notes/servu_15-2-3_release_notes.htm


About Trustwave:
Trustwave helps businesses fight cybercrime, protect data and reduce security 
risk. With cloud and managed security services, integrated technologies and a 
team of security experts, ethical hackers and researchers, Trustwave enables 
businesses to transform the way they manage their information security and 
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automated, efficient and cost-effective threat, vulnerability and compliance 
management. Trustwave is headquartered in Chicago, with customers in 96 
countries. For more information about Trustwave, visit 
https://www.trustwave.com.

About Trustwave SpiderLabs:
SpiderLabs(R) is the advanced security team at Trustwave focused on
application security, incident response, penetration testing, physical
security and security research. The team has performed over a thousand
incident investigations, thousands of penetration tests and hundreds of
application security tests globally. In addition, the SpiderLabs Research
team provides intelligence through bleeding-edge research and proof of
concept tool development to enhance Trustwave's products and services.
https://www.trustwave.com/spiderlabs

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implied, including the warranties of merchantability and fitness for a
particular purpose. In no event shall Trustwave or its suppliers be liable
for any damages whatsoever including direct, indirect, incidental,
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